chore: replace left-over occurences of exa with eza where meaningful

[zohnannor]

what was NOT changed (invisible in diff):

$ rg 'exa[^cm]' -iC2 --sort=path
CHANGELOG.md
1804-
1805:- Replace left-over exa in fish completion
1806-- Diabling static linked binaries due to segfault
--
1890-- Add rustfmt.toml file to prevent flags.rs fmt on save
1891:- Add quotations around filenames with spaces. exa pr#1165
1892-- Replace hardcoded version by version variable
--
1950-
1951:- Add EXA_COLOR bindings for un-themed items
1952:- Add EZA_ environment variables with fallback to EXA_
1953-- Listing files only using '--only-files' flag
--
2056-- Generate device files
2057:- Add unit tests that test both exa and ls style codes together
2058-- Address variable names
--
2299-- Use perfect hash tables for file types and icons
2300:- Add backlog of icons from various exa pull requests and others
2301:- Add backlog of icons from various exa issues
2302-
--
2386-- Add missing colon before -w/--width
2387:- Replace exa by eza in help string
2388:- Change exa to eza in invalid option error
2389-- Add missing name section to eza_colors-explanation manpage
2390:- Replace exa by eza in .gitignore
2391-
--
2567-- Rename eza-colors-explanation
2568:- Exa -> eza in manpage
2569-
--
2799-
2800:- Add hint how to install exa on Android / Termux
2801-

INSTALL.md
163-
164:If `exa` was installed before, replace it with `eza`:
165-```shell

README.md
49-
50:**eza** features not in exa (non-exhaustive):
51-
52:- Fixes [“The Grid Bug”](https://github.com/eza-community/eza/issues/66#issuecomment-1656758327) introduced in exa 2021.
53-- Hyperlink support.

man/eza.1.md
300-
301:If an environment variable prefixed with `EZA_` is not set, for backward compatibility, it will default to its counterpart starting with `EXA_`.
302-
--
392-
393:Our infinite thanks to Benjamin ‘ogham’ Sago and all the other contributors of exa, from which eza was forked.
394-

man/eza_colors.5.md
26-
27:For backwards compatibility `EXA_COLORS` environment variables is checked if `EZA_COLORS` is unset.
28-
--
395-
396:Our infinite thanks to Benjamin ‘ogham’ Sago and all the other contributors of exa, from which eza was forked.
397-

src/main.rs
62-        env::var_os(vars::EZA_DEBUG)
63:            .or_else(|| env::var_os(vars::EZA_DEBUG).or_else(|| env::var_os(vars::EXA_DEBUG))),
64-    );

src/options/file_name.rs
65-    fn get_width<V: Vars>(vars: &V) -> Result<u32, OptionsError> {
66:        vars.get_with_fallback(vars::EZA_ICON_SPACING, vars::EXA_ICON_SPACING)
67-            .map(|s| s.to_string_lossy().to_string())
--
71-                    let source = NumberSource::Env(
72:                        vars.source(vars::EZA_ICON_SPACING, vars::EXA_ICON_SPACING)
73-                            .unwrap_or("1"),

src/options/mod.rs
161-        let strict = vars
162:            .get_with_fallback(vars::EZA_STRICT, vars::EXA_STRICT)
163-            .is_some();

src/options/theme.rs
87-        let eza = vars
88:            .get_with_fallback(vars::EZA_COLORS, vars::EXA_COLORS)
89-            .map(|e| e.to_string_lossy().to_string());

src/options/vars.rs
32-pub static EZA_COLORS: &str = "EZA_COLORS";
33:pub static EXA_COLORS: &str = "EXA_COLORS";
34-
--
40-pub static EZA_STRICT: &str = "EZA_STRICT";
41:pub static EXA_STRICT: &str = "EXA_STRICT";
42-
--
45-pub static EZA_DEBUG: &str = "EZA_DEBUG";
46:pub static EXA_DEBUG: &str = "EXA_DEBUG";
47-
--
51-pub static EZA_GRID_ROWS: &str = "EZA_GRID_ROWS";
52:pub static EXA_GRID_ROWS: &str = "EXA_GRID_ROWS";
53-
--
58-pub static EZA_ICON_SPACING: &str = "EZA_ICON_SPACING";
59:pub static EXA_ICON_SPACING: &str = "EXA_ICON_SPACING";
60-
61-pub static EZA_OVERRIDE_GIT: &str = "EZA_OVERRIDE_GIT";
62:pub static EXA_OVERRIDE_GIT: &str = "EXA_OVERRIDE_GIT";
63-
--
66-pub static EZA_MIN_LUMINANCE: &str = "EZA_MIN_LUMINANCE";
67:pub static EXA_MIN_LUMINANCE: &str = "EXA_MIN_LUMINANCE";
68-
--
127-            match name {
128:                "EXA_STRICT" | "EZA_STRICT" if !self.strict.is_empty() => Some(self.strict.clone()),
129:                "EZA_COLORS" | "LS_COLORS" | "EXA_COLORS" if !self.colors.is_empty() => {
130-                    Some(self.colors.clone())
131-                }
132:                "EXA_DEBUG" | "EZA_DEBUG" if !self.debug.is_empty() => Some(self.debug.clone()),
133:                "EXA_GRID_ROWS" | "EZA_GRID_ROWS" if !self.grid_rows.is_empty() => {
134-                    Some(self.grid_rows.clone())
135-                }
136:                "EXA_ICON_SPACING" | "EZA_ICON_SPACING" if !self.icon_spacing.is_empty() => {
137-                    Some(self.icon_spacing.clone())
138-                }
139:                "EXA_MIN_LUMINANCE" | "EZA_MIN_LUMINANCE" if !self.luminance.is_empty() => {
140-                    Some(self.luminance.clone())
--
153-            match var {
154:                "EXA_STRICT" | "EZA_STRICT" => self.strict = value.clone(),
155:                "EZA_COLORS" | "LS_COLORS" | "EXA_COLORS" => self.colors = value.clone(),
156:                "EXA_DEBUG" | "EZA_DEBUG" => self.debug = value.clone(),
157:                "EXA_GRID_ROWS" | "EZA_GRID_ROWS" => self.grid_rows = value.clone(),
158:                "EXA_ICON_SPACING" | "EZA_ICON_SPACING" => self.icon_spacing = value.clone(),
159:                "EXA_MIN_LUMINANCE" | "EZA_MIN_LUMINANCE" => self.luminance = value.clone(),
160-                "EZA_ICONS_AUTO" => self.icons = value.clone(),

src/options/view.rs
214-    fn deduce<V: Vars>(vars: &V) -> Result<Self, OptionsError> {
215:        vars.get_with_fallback(vars::EZA_GRID_ROWS, vars::EXA_GRID_ROWS)
216-            .and_then(|s| s.into_string().ok())
--
220-                    let source = NumberSource::Env(
221:                        vars.source(vars::EZA_GRID_ROWS, vars::EXA_GRID_ROWS)
222-                            .unwrap(),
--
253-        let no_git_env = vars
254:            .get_with_fallback(vars::EZA_OVERRIDE_GIT, vars::EXA_OVERRIDE_GIT)
255-            .is_some();
--
498-        let min_luminance = vars
499:            .get_with_fallback(vars::EZA_MIN_LUMINANCE, vars::EXA_MIN_LUMINANCE)
500-            .map_or(40, |var| match var.to_string_lossy().parse() {