fix: correctly determine bind:group members

[dummdidumm]

• Previously, any each block parents were used as keys for the sub group. That's wrong, it should only be using each blocks whos declarations contribute to the bind:group expression. Fixes Svelte 5: Nested {#each} causes bind:group to improperly clear #10345
• Only the left-most identifier of the expression was used to determine the binding group. This is wrong, all identifiers within the expression need to be taken into account. Fixes Svelte 5: bind:group incorrectly considers other groups when changing value #9947

Before submitting the PR, please make sure you do the following

• It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs
• Prefix your PR title with feat:, fix:, chore:, or docs:.
• This message body should clearly illustrate what problems it solves.
• Ideally, include a test that fails without this PR but passes with it.

Tests and linting

• Run the tests with pnpm test and lint the project with pnpm lint

[changeset-bot]

🦋 Changeset detected

Latest commit: 7a2d201

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

This PR includes changesets to release 1 package

Name	Type
svelte	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR