[Backport 2.x] [Next Theme] Make next theme the default

[opensearch-trigger-bot]

Backport 9d7f576 from #4854.

[codecov]

Codecov Report

Merging #4887 (efbfdee) into 2.x (921263a) will decrease coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##              2.x    #4887      +/-   ##
==========================================
- Coverage   66.46%   66.44%   -0.03%     
==========================================
  Files        3396     3396              
  Lines       64847    64847              
  Branches    10356    10356              
==========================================
- Hits        43100    43086      -14     
- Misses      19190    19203      +13     
- Partials     2557     2558       +1     

Flag	Coverage Δ
Linux_1	34.91% <100.00%> (ø)
Linux_2	55.18% <ø> (ø)
Linux_3	44.19% <100.00%> (-0.02%)	⬇️
Linux_4	35.08% <100.00%> (ø)
Windows_1	34.93% <100.00%> (-0.05%)	⬇️
Windows_2	55.15% <ø> (ø)
Windows_3	44.20% <100.00%> (ø)
Windows_4	35.08% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
src/core/server/ui_settings/settings/theme.ts	100.00% <ø> (ø)
src/core/server/ui_settings/ui_settings_config.ts	100.00% <ø> (ø)
packages/osd-ui-shared-deps/theme.ts	41.66% <100.00%> (ø)

... and 2 files with indirect coverage changes

[kavilla]

I forgot to check do we need to add the migration to force people onto this if their config has this set?

I think we cleared it out anyways in a previously release so it's likely an edge case.

[joshuarrrr]

I forgot to check do we need to add the migration to force people onto this if their config has this set?

I think we cleared it out anyways in a previously release so it's likely an edge case.

This may be something we need to do. I'll test it out later this afternoon.