language: Select language based on longest matching path extension (#29716)

Closes #8408  
Closes #10997

This is a reboot of [my original
PR](https://github.com/zed-industries/zed/pull/11697) from last year. I
believe that I've addressed all the comments raised in that original
review, but Zed has changed a lot in the past year, so I'm sure there
will be some new stuff to consider too.

- updates the language matching and lookup to consider not just "does
the suffix/glob match" but also "... and is it the longest such match"
- adds a new `LanguageCustomFileTypes` struct to pass user globs from
settings to the registry
- _minor/unrelated:_ updates a test for the JS extension that wasn't
actually testing what is intended to
- _minor/unrelated:_ removed 2 redundant path extensions from the JS
lang extension

**Languages that may use this**

- Laravel Blade templates use the `blade.php` compound extension
-
[apparently](https://github.com/zed-industries/zed/issues/10765#issuecomment-2091293304)
Angular uses `component.html`
  - see also https://github.com/zed-industries/extensions/issues/169
- _hypothetically_ someone could publish a "JS test" extension w/ custom
highlights and/or snippets; many JS tests use `test.js` or `spec.js`

**Verifying these changes**

I added a number of assertions for this new behavior, and I also
confirmed that the (recently patched) [Laravel Blade
extension](https://github.com/bajrangCoder/zed-laravel-blade) opens as
expected for `blade.php` files, whereas on `main` it does not.

cc @maxbrunsfeld (reviewed my original PR last year), @osiewicz and
@MrSubidubi (have recently been in this part of the code)

Release Notes:

- Added support for "compound" file extensions in language extensions,
such `blade.php` and `component.html`. Closes #8408 and #10997.

crates/languages/src/typescript/config.toml

@@ -1,6 +1,6 @@
 name = "TypeScript"
 grammar = "typescript"
-path_suffixes = ["ts", "cts", "d.cts", "d.mts", "mts"]
+path_suffixes = ["ts", "cts", "mts"]
 first_line_pattern = '^#!.*\b(?:deno run|ts-node|bun|tsx)\b'
 line_comments = ["// "]
 block_comment = ["/*", "*/"]