Release preparation for version 2.21.0

[codeql-ci]

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[Copilot]

Pull Request Overview

This PR prepares for the upcoming release by updating version numbers and corresponding changelog and release note entries across multiple CodeQL packs for C#, C++, and GitHub Actions.

• Updated version references in configuration files and release note files.
• Added new release note files and appended entries to changelogs.
• Removed obsolete change note content for a redundant ATL fix.

Reviewed Changes

Copilot reviewed 203 out of 203 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
csharp/ql/campaigns/Solorigate/lib/codeql-pack.release.yml	Updated lastReleaseVersion from 1.7.36 to 1.7.37
csharp/ql/campaigns/Solorigate/lib/change-notes/released/1.7.37.md	Added release notes for version 1.7.37
csharp/ql/campaigns/Solorigate/lib/CHANGELOG.md	Added changelog entry for release 1.7.37
cpp/ql/src/qlpack.yml	Renamed version from 1.3.7-dev to 1.3.7
cpp/ql/src/codeql-pack.release.yml	Updated lastReleaseVersion from 1.3.6 to 1.3.7
cpp/ql/src/change-notes/released/1.3.7.md	Introduced detailed release notes for version 1.3.7
cpp/ql/src/change-notes/2025-03-14-mad-atl-fix.md	Removed redundant ATL fix release note
cpp/ql/src/CHANGELOG.md	Added changelog entry for release 1.3.7
cpp/ql/lib/qlpack.yml	Upgraded version from 4.0.4-dev to 4.1.0
cpp/ql/lib/codeql-pack.release.yml	Updated lastReleaseVersion from 4.0.3 to 4.1.0
cpp/ql/lib/change-notes/released/4.1.0.md	Added release notes for version 4.1.0 with new feature details
cpp/ql/lib/CHANGELOG.md	Appended changelog entry for release 4.1.0
actions/ql/src/qlpack.yml	Updated version from 0.5.3-dev to 0.5.3
actions/ql/src/codeql-pack.release.yml	Updated lastReleaseVersion from 0.5.2 to 0.5.3
actions/ql/src/change-notes/released/0.5.3.md	Added release notes for version 0.5.3 addressing typo fixes
actions/ql/src/CHANGELOG.md	Enhanced changelog with 0.5.3 release details and updated Immutable Actions messaging
actions/ql/lib/qlpack.yml	Updated version from 0.4.6-dev to 0.4.6
actions/ql/lib/codeql-pack.release.yml	Updated lastReleaseVersion from 0.4.5 to 0.4.6
actions/ql/lib/change-notes/released/0.4.6.md	Added release notes for version 0.4.6 regarding bug fixes for injection alerts
actions/ql/lib/CHANGELOG.md	Appended changelog entry for release 0.4.6

Comments suppressed due to low confidence (2)

actions/ql/src/CHANGELOG.md:17

• [nitpick] Consider revising the wording for the Immutable Actions update to ensure users understand the implications of the query being moved to the experimental folder.

Immutable Actions feature is not yet available for customer use. The query has also been moved to the experimental folder and will not be used in code scanning unless it is explicitly added to a code scanning configuration.

cpp/ql/src/change-notes/2025-03-14-mad-atl-fix.md:1

• Before removing the legacy ATL fix release note, verify that no important historical context is lost or that the information is appropriately archived elsewhere.

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