Prepare PL 3.8 Release

[felixarntz]

This issue is to track preparation of the upcoming 3.8.0 release up until publishing, which is due January 27, 2025.

• Create release/3.8.0 branch closer to the release date
• Finalize scope and punt unfinished pull requests to following release (Thursday, January 23, 2025)
• Bump versions in milestones according to the scope (Thursday, January 23, 2025)
• Smoke test (Friday, January 24, 2025)
• Prepare the release (Tuesday, January 27, 2025)

Note: The release would normally happen on Monday January 20, but due to a US holiday several folks from the team that handle the releases are out, which is why the release is postponed to the day after.

Update: Due the holiday and the fact that several milestones are not yet cleared, the release has been postponed to the following Monday.