[ML] Anomaly Detection: Consolidate severity colors

[walterra]

Summary

Part of #140695.

We defined the hex codes for anomaly detection severity colors in several places. This PR consolidates this and makes sure the hex codes are defined in just one place. Note this PR doesn't change any of the colors or styling related to anomaly detection, it is pure refactoring to make future updates to these colors more easy.

• Renames BLANK to UNKNOWN to be in line with severity labels.
• Uses ML_SEVERITY_COLORS.* in test assertions so future color changes won't need updating every assertion.
• Migrates all SCSS that made use of severity colors to emotion so it can reuse ML_SEVERITY_COLORS. Therefor the SCSS based severity colors get removed in this PR.

Checklist

• The PR description includes the appropriate Release Notes section, and the correct release_note:* label is applied per the guidelines

[elasticmachine]

Pinging @elastic/ml-ui (:ml)

[peteharverson]

LGTM

[elasticmachine]

💔 Build Failed

• Buildkite Build
• Commit: 773a9df

Failed CI Steps

• Serverless Rule Management - Prebuilt Rules - Security Solution Cypress Tests #1

Metrics [docs]

Module Count

Fewer modules leads to a faster build time

id	before	after	diff
securitySolution	6435	6436	+1

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
apm	3.3MB	3.3MB	+8.0B
ml	4.7MB	4.7MB	-6.9KB
uptime	467.4KB	467.4KB	+8.0B
total			-6.9KB

History

• 💔 Build #262224 failed 7ce2e2b
• 💔 Build #262190 failed 5543553
• 💔 Build #261964 failed 5543553

cc @walterra

[rbrtj]

Overall LGTM, left some notes

[rbrtj]

Suggestion to update the function description above

Suggested change

	Returns a severity RGB color (one of critical, major, minor, warning, low or unknown)

unknown instead of blank

[walterra]

Thanks for spotting this, updated in 98d1a09.

[rbrtj]

MINOR and MAJOR are slightly different here (than #ffdd00 and #ff7e00), but I assume this is intentional?

[walterra]

Again thanks for your attention to detail! Discussed with Pete and we can't remember if this was intentional or an oversight originally, so we'll move forward with the consolidation to make it the same color.

[rbrtj]

Just noting, it might be intentional as well but ML_SEVERITY_COLORS.LOW is different than mlColors.lowWarning

[walterra]

Same as the other, comment above, not sure if this was intentional or oversight way back.