fix(wgsl-in): Handle Unterminated Block Comments

[BKDaugherty]

Adds a new token to keep track of unterminated block comments in order to emit an error to the user highlighting the offending unterminated block comment.

Connections
Link to the issues addressed by this PR, or dependent PRs in other repositories

#8877 (comment)

When one pull request builds on another, please put "Depends on
#NNNN" towards the top of its description. This helps maintainers
notice that they shouldn't merge it until its ancestor has been
approved. Don't use draft PR status to indicate this.

Description
Describe what problem this is solving, and how it's solved.

Block comments that aren't terminated before this changeset were lexed as Token::End. This didn't give the parser enough information to report an error.

This PR introduces a new token so that this can be tracked, and reports errors when an unterminated block comment is found.

Testing
Explain how this change is tested.

This CTS test passes now. I also wrote tests.

[INFO  wgpu_xtask::cts] Running CTS
[INFO  wgpu_xtask::cts] Running webgpu:shader,validation,parse,comments:unterminated_block_comment:terminated=false
$ /Users/brendon/Dev/wgpu/target/debug/cts_runner ./tools/run_deno --verbose webgpu:shader,validation,parse,comments:unterminated_block_comment:terminated=false
[pass] webgpu:shader,validation,parse,comments:unterminated_block_comment:terminated=false (348ms). Log:
  - (in subcase: ) INFO: subcase ran

** Summary **
Passed  w/o warnings = 1 / 1 = 100.00%
Passed with warnings = 0 / 1 =   0.00%
Skipped              = 0 / 1 =   0.00%
Failed               = 0 / 1 =   0.00%

Squash or Rebase?

Squash.

If your pull request contains multiple commits, please indicate whether
they need to be squashed into a single commit before they're merged,
or if they're ready to rebase onto trunk as they stand. In the
latter case, please ensure that each commit passes all CI tests, so
that we can continue to bisect along trunk to isolate bugs.

Checklist

• Run cargo fmt.
• Run taplo format.
• Run cargo clippy --tests. If applicable, add:
  • --target wasm32-unknown-unknown
• Run cargo xtask test to run tests.
• If this contains user-facing changes, add a CHANGELOG.md entry.

[ErichDonGubler]

Looks great! Just a couple of minor things that we can fix (if they're easy) before merging.

[ErichDonGubler]

style: Let's add backticks so the actual code being suggested is clear, like so:

Suggested change

	"must be closed with */".into(),
	"must be closed with `*/`".into(),

[ErichDonGubler]

Fixed as suggested as a fixup! commit (510f538). LMK if this looks okay to you.

[BKDaugherty]

Yeah looks great! Thanks for doing that!

[ErichDonGubler]

Not sure what's going on with the CHANGELOG check, but it's got something to do with Git. I bet if you rebase, it'll clear up.

[BKDaugherty]

Thanks for the quick review and fixes @ErichDonGubler!