feat: allow $state in computed class fields

[Ocean-OS]

Closes #17012.
As described here, the way we transform computed class fields is using a variable to deduplicate the key (to avoid side effects and the like):

// before
let i = 0;
class Foo {
  [i++] = $state(0);
}
// after
let i = 0;
var Foo = (() => {
  let key;
  return class Foo {
    #_ = $.state(0);
    get [key = i++]() {
      return $.get(this.#_);
    }
    set [key]($$value) {
      return $.set(this.#_, $$value, true);
    }
  }
})();

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[changeset-bot]

🦋 Changeset detected

Latest commit: 307e42f

The changes in this PR will be included in the next version bump.

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svelte	Minor

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[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-svelte-17022-svelte.vercel.app/

[github-actions]

Playground

pnpm add https://pkg.pr.new/svelte@17022

[dangodai]

This predates your change, but it looks like the second condition (true) is from a leftover TODO that never came to fruition? There are 2 more copies of it now in this file. (I was bothered by it when reading the source, just not enough to make a PR for it 😅 )

Also looks like at least member and should_proxy can be de-duplicated and shared between computed and non-computed branches.