Consolidate browser compatibility data, drop IE11 support

[rtibbles]

Summary

• Consolidates browser compatibility data so that we use the same source of truth for browserslist and checking supported browsers in the frontend
• Drops IE11 support
• Updates deprecation warnings about IE11 for browsing users to give upgrade warning instead

References

Fixes #5336

Reviewer guidance

The only other place I could find IE11 specific code was in the TextTruncatorCSS component, but I was not entirely sure how to remove the IE11 specific code. Advice from @MisRob would be appreciated, or we can file a follow up issue for this cleanup.

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Testing checklist

• Contributor has fully tested the PR manually
• If there are any front-end changes, before/after screenshots are included
• Critical user journeys are covered by Gherkin stories
• Critical and brittle code paths are covered by unit tests

PR process

• PR has the correct target branch and milestone
• PR has 'needs review' or 'work-in-progress' label
• If PR is ready for review, a reviewer has been added. (Don't use 'Assignees')
• If this is an important user-facing change, PR or related issue has a 'changelog' label
• If this includes an internal dependency change, a link to the diff is provided

Reviewer checklist

• Automated test coverage is satisfactory
• PR is fully functional
• PR has been tested for accessibility regressions
• External dependency files were updated if necessary (yarn and pip)
• Documentation is updated
• Contributor is in AUTHORS.md

[github-actions]

Build Artifacts

Asset type	Download link
PEX file	kolibri-0.16.0b10.dev0_git.469.gdc9494ab.pex
Windows Installer (EXE)	kolibri-0.16.0b10.dev0+git.469.gdc9494ab-unsigned.exe
Debian Package	kolibri_0.16.0b10.dev0+git.469.gdc9494ab-0ubuntu1_all.deb
Mac Installer (DMG)	kolibri-0.16.0b10.dev0+git.469.gdc9494ab-0.3.0.dmg
Android Package (APK)	kolibri-0.16.0b10.dev0+git.469.gdc9494ab-0.1.0-debug.apk
TAR file	kolibri-0.16.0b10.dev0+git.469.gdc9494ab.tar.gz
WHL file	kolibri-0.16.0b10.dev0+git.469.gdc9494ab-py2.py3-none-any.whl

[marcellamaki]

The changes seem okay, but the browser requirements code is hard to follow. Added a comment about what in particular tripped me up, but happy to chat further about what might help

[rtibbles]

Have updated to try to make the parsing logic more self explanatory.

[marcellamaki]

Thanks for breaking this down - I find it much easier to comprehend. Per slack discussion, we'll go forward with this and check in with @MisRob re: TextTruncator and address in a follow up issue as appropriate

[rtibbles]

Follow up will happen in KDS where KTextTruncator has been implemented.

[rtibbles]

Docs build failure is unrelated, merging.