[Console][Monaco] Fix low contrast colors in selected text on Manoco Console

[sakurai-youhei]

Summary

This PR changes the background colors to increase the contrast of neighboring colors on the Manoco Console.

Fixes #186772

Colors in this PR:

Colors before this PR:

Colors on 8.4.1:

Checklist

• Any UI touched in this PR does not create any new axe failures (run axe in browser: FF, Chrome)
• This renders correctly on smaller devices using a responsive layout. (You can test this in your browser)
• This was checked for cross-browser compatibility

For maintainers

• This was checked for breaking API changes and was labeled appropriately

[sakurai-youhei]

@elasticmachine merge upstream

[kibana-ci]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: 2e0991d

Failed CI Steps

Metrics [docs]

Page load bundle

Size of the bundles that are downloaded on every page load. Target size is below 100kb

id	before	after	diff
kbnUiSharedDeps-srcJs	3.2MB	3.2MB	+102.0B

History

• 💛 Build #217370 was flaky a5e8a65

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@elasticmachine merge upstream

[MichaelMarcialis]

@ryankeairns: Do the color changes being proposed here align with the colors you're proposing for the ES|QL Monaco editor? If not, should they be for consistency?

[ryankeairns]

@ryankeairns: Do the color changes being proposed here align with the colors you're proposing for the ES|QL Monaco editor? If not, should they be for consistency?

For the ES|QL editor, I believe we leave the selection background color to your system default... although, that can produce some not great contrast, too. This feels a bit more full proof and could be done for ES|QL too - I'll track that.

As for the background colors - we used EUI theme variables over there, perhaps that can/should be done here too?
Referring to the color settings here: https://github.com/elastic/kibana/blob/main/packages/kbn-monaco/src/esql/lib/esql_theme.ts

[sakurai-youhei]

I'm closing this PR in favor of #189060