Method refactor

[andrevidela]

Description

Prerequisite for #3615

• replace Method
• harmonise and merge Signature and Declaration
• replace (String, Name) by WithData [Doc', FC'] Name

[mattpolzin]

Looks like there are some places where you've chosen val . name or .name.val over .nameVal -- I'm guessing that was arbitrary and it may make sense to refactor to use the helper everywhere it is applicable. Not a big deal to me though.

[andrevidela]

the nameVal helper was actually a necessary change because.name.val was too complicated to disambiguate in the cases where .nameVal is present.
I'm not sure what to make of this in that I don't think it makes sense to change all the instances of .name.val but I also don't feel like .nameVal should even be necessary

[mattpolzin]

The changes look sane to me, but ideally this PR is left open a bit longer in case someone with more experience with the compiler internals than me sees something that could regress performance or be a breaking change downstream.

[dunhamsteve]

Looks good to me.