feat: Introduce gutenberg_kit editor session property

[dcalhoun]

Enable analysis of editor sessions utilizing GutenbergKit.

Related:

• https://github.com/Automattic/dotcom-forge/issues/8268.
• feat: Improve editor session events WordPress-iOS#23955
• feat: Communicate editor load event to host app GutenbergKit#54

To Test:

1. Launch the experimental editor.
2. Close the editor.
3. Verify editor_session_start|end events trigger with an editor: gutenberg_kit property value.

Regression Notes

1. Potential unintended areas of impact
   Disruption to events within other text editors.
2. What I did to test those areas of impact (or what existing automated tests I relied on)
   Verified the editor session events continue working as expected.
3. What automated tests I added (or what prevented me from doing so)
   Deemed unnecessary for this experimental editor analytic event.

PR Submission Checklist:

• I have completed the Regression Notes.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

Testing Checklist (strike-out the not-applying and unnecessary ones):

• WordPress.com sites and self-hosted Jetpack sites.
• Portrait and landscape orientations.
• Light and dark modes.
• Fonts: Larger, smaller and bold text.
• High contrast.
• Talkback.
• Languages with large words or with letters/accents not frequently used in English.
• Right-to-left languages. (Even if translation isn’t complete, formatting should still respect the right-to-left layout)
• Large and small screen sizes. (Tablet and smaller phones)
• Multi-tasking: Split screen and Pop-up view. (Android 10 or higher)

[dangermattic]

	1 Warning
⚠️	PR is not assigned to a milestone.

Generated by 🚫 Danger

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress by scanning the QR code below to install the corresponding build.

	App Name	WordPress
	Flavor	Jalapeno
	Build Type	Debug
	Version	pr21564-12fa0d8
	Commit	12fa0d8
	Direct Download	wordpress-prototype-build-pr21564-12fa0d8.apk

Note: Google Login is not supported on these builds.

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack by scanning the QR code below to install the corresponding build.

	App Name	Jetpack
	Flavor	Jalapeno
	Build Type	Debug
	Version	pr21564-12fa0d8
	Commit	12fa0d8
	Direct Download	jetpack-prototype-build-pr21564-12fa0d8.apk

Note: Google Login is not supported on these builds.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 39.48%. Comparing base (108babf) to head (12fa0d8).
Report is 2 commits behind head on trunk.

Additional details and impacted files

@@           Coverage Diff           @@
##            trunk   #21564   +/-   ##
=======================================
  Coverage   39.48%   39.48%           
=======================================
  Files        2117     2117           
  Lines       99464    99464           
  Branches    15296    15296           
=======================================
  Hits        39269    39269           
  Misses      56714    56714           
  Partials     3481     3481           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[nbradbury]

Changes are good!