Backports of Prototype fixes from 2.417 to stable-2.414

[basil]

This PR contains backports of #8280, #8279, #8278, and #8307 (all delivered one week ago in 2.417) to stable-2.414. The reason for this proposal is to make 2.414.1 a solid LTS baseline for plugins to depend on in the post-Prototype transition, with all known Prototype fixes integrated to core. While the four mentioned PRs are code cleanup PRs rather than bug fixes, I think it is worth backporting them so that plugins that require a recent LTS baseline (e.g. for #8008) have one they can depend on that is consistent with weeklies. There are no reported regressions with the above 4 PRs.

Testing done

None, other than the PR build for this PR.

Proposed changelog entries

N/A

Proposed upgrade guidelines

N/A

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1. The Jira issue, if it exists, is well-described.
2. The changelog entries and upgrade guidelines are appropriate for the audience affected by the change (users or developers, depending on the change) and are in the imperative mood (see examples). Fill in the Proposed upgrade guidelines section only if there are breaking changes or changes that may require extra steps from users during upgrade.
3. There is automated testing or an explanation as to why this change has no tests.
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5. New deprecations are annotated with @Deprecated(since = "TODO") or @Deprecated(forRemoval = true, since = "TODO"), if applicable.
6. New or substantially changed JavaScript is not defined inline and does not call eval to ease future introduction of Content Security Policy (CSP) directives (see documentation).
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8. For new APIs and extension points, there is a link to at least one consumer.

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@mention

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2. Conversations in the pull request are over, or it is explicit that a reviewer is not blocking the change.
3. Changelog entries in the pull request title and/or Proposed changelog entries are accurate, human-readable, and in the imperative mood.
4. Proper changelog labels are set so that the changelog can be generated automatically.
5. If the change needs additional upgrade steps from users, the upgrade-guide-needed label is set and there is a Proposed upgrade guidelines section in the pull request title (see example).
6. If it would make sense to backport the change to LTS, a Jira issue must exist, be a Bug or Improvement, and be labeled as lts-candidate to be considered (see query).

[MarkEWaite]

I think this is the right change. We want the Prototype.js code consistent between weekly and LTS

[timja]

Sure