fix: correct variable invalidation with bind handler

[discapes]

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Tests

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As per #7704:

This pull request removes behaviour that

• was intended to fix issue Bindings don't work inside {#each reactiveThing as thing} #2444
• no longer works as it's supposed to
• is undocumented and handles only a specific case (the assignment happens in a reactive declaration)
• causes other bugs, see Bind handler incorrectly invalidates other variables. #7704

[discapes]

I initially thought that the removed code was useless, since the demo that it intended to fix does not work (the one in #2444. However, after running the tests, I found that the reason that it did not work didn't affect the tests. The reason is that the reactive declarations that depend on todos are removed, which I suspect is because while optimizing the compiler assumes todos never changes directly so is never invalidated, failing to take into account that todos might be invalidated as a result of the behaviour of renderer_invalidate. I will make changes so that the test pass, which means implementing the checks I talked about in #7704. A new issue should be raised about the demo not working.

[baseballyama]

Thank you for the PR!
I have not deep dive into this yet, but we need to add tests!

[baseballyama]

I run REPL of #7704 with this PR locally, but I think it doesn't fix.

Could you explain what issue will be solved by this PR? @discapes

And I think such reactive issues will be handled in Svelte4. not Svelte3.
see: #7416 (comment)

[dummdidumm]

Closing since we don't really know what's this about and there is no test