Add support for experimental features in the parsing phase

[ironcev]

Description

This PR brings support for experimental features to the parsing phase. This is needed so that we can support use cases like, e.g., adding new language keywords behind a feature flag.

A concrete example would be the panic keyword added in #7073. The parsing of the panic token differs if it is interpreted as a keyword (when the error_type experimental feature is active) or as a regular identifier (when error_type is off).

Because ExperimentalFeatures are needed in the Parse::parse(parser: &mut Parser) methods, the Parser got extended with the experimental field.

The consequence of bringing the ExperimentalFeatures to the parsing phase is, that swayfmt and forc fmt can also require an experimental feature to be set, to properly parse a project. In those tools, ExperimentalFeatures are passed as a field on the Formatter.

Note that this PR does not put the provided experimental flags into use. The first concrete usage will be in #7073.

This PR is a prerequisite for #7073.

Checklist

• I have linked to any relevant issues.
• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation where relevant (API docs, the reference, and the Sway book).
  • If my change requires substantial documentation changes, I have requested support from the DevRel team
• I have added tests that prove my fix is effective or that my feature works.
• I have added (or requested a maintainer to add) the necessary Breaking* or New Feature labels where relevant.
• I have done my best to ensure that my PR adheres to the Fuel Labs Code Review Standards.
• I have requested a review from the relevant team or maintainers.

[codspeed-hq]

CodSpeed Performance Report

Merging #7124 will not alter performance

_{Comparing ironcev/experimental-features-in-parsing (a5317f3) with master (eb57cbf)}

Summary

✅ 22 untouched benchmarks