fix(tests)!: make typed temporal test literals unquoted

[benbellick]

Quoted date/time-shaped values are ambiguous in the test grammar. The old lexer matched values like '2020-05-10' as DateLiteral before the parser could see that the argument was annotated as ::str.

This resulted in cases like identity('2020-05-10'::str) = '2020-05-10'::str failing to parse with mismatched input 'str' expecting 'DATE'. Because '2020-05-10' is lexed as DateLiteral instead of StringLiteral, it fails the stringArg rule:

stringArg
    : StringLiteral DoubleColon stringType
    ;

To fix this, typed temporal and interval literals are now unquoted, so quoted values are always available as strings. Concretely, tests like:

lt('2020-12-30'::date, '2020-12-31'::date) = true::bool

instead become:

lt(2020-12-30::date, 2020-12-31::date) = true::bool

Existing datetime tests have been updated to use the unquoted form.

Alternatives

I first tried adding a shared quotedLiteral parser rule and allowing stringArg to accept date/time/interval tokens. That was smaller and backwards compatible, but it left the grammar treating string arguments as date/time tokens in some cases. Making typed temporal literals unquoted removes the ambiguity instead.

Breaking Change

I am unsure if this should be treated as breaking. It breaks the scalar function test format, but not the Substrait format itself.

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Note: This PR was developed with AI assistance. All changes have been reviewed, and I take full responsibility for this contribution.

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