fix: Class decorator correctly passes return value

[liuxingbaoyu]

Q	A
Fixed Issues?	Fixes #16198
Patch: Bug Fix?	√
Major: Breaking Change?
Minor: New Feature?
Tests Added + Pass?	√
Documentation PR Link
Any Dependency Changes?
License	MIT

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Edit by @JLHwung

In this PR we fix a regression introduced in #16160. Currently when multiple class decorators are applied, they are provided with the unmodified classes, this is incorrect as per 15.7.7 ApplyDecoratorsToClassDefinition step 1.e, the next decorator should be applied on the modified class.

[babel-bot]

Build successful! You can test your changes in the REPL here: https://babeljs.io/repl/build/56084/

[JLHwung]

Can we rename the test case to decorator-access-modified-classes? We already have decorator-access-modified-{fields,methods} for the same purposes.

[JLHwung]

I updated the PR's description, I hope it can help reviewers pick up the PR's intention. Please do fill in the descriptions in the PR template, it will also help our future selves when trying to understand why changes are made.

[liuxingbaoyu]

Thanks!
In fact, the detailed description of the issue exists in #16198, and this PR only has small changes, and the added tests also help with review, so I did not add a detailed description. :)
The section on specs is really helpful, but I actually did this by comparing the code before regression was introduced.🤦‍♂️

[nicolo-ribaudo]

👍

[JLHwung]

CI error is not related.