[Lens] Heatmap expression types improvement.

[Kuznietsov]

Summary

Completes part of #140555

Changed types for Heatmap toExpression function in Lens.

⚠️ Fixed heatmap preview if no value was passed.

[elasticmachine]

Pinging @elastic/kibana-vis-editors @elastic/kibana-vis-editors-external (Team:VisEditors)

[Kuznietsov]

@elastic/kibana-vis-editors, could you, please, review this PR? Thanks 😃

[stratoula]

Changes LGTM! Did a brief testing on Lens heatmaps, everything seems to work fine

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: 805ec64

Metrics [docs]

Public APIs missing comments

Total count of every public API that lacks a comment. Target amount is 0. Run node scripts/build_api_docs --plugin [yourplugin] --stats comments for more detailed information.

id	before	after	diff
expressionHeatmap	104	107	+3

Async chunks

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

id	before	after	diff
lens	1.3MB	1.3MB	-102.0B

Public APIs missing exports

Total count of every type that is part of your API that should be exported but is not. This will cause broken links in the API documentation system. Target amount is 0. Run node scripts/build_api_docs --plugin [yourplugin] --stats exports for more detailed information.

id	before	after	diff
expressionHeatmap	3	2	-1

Unknown metric groups

API count

id	before	after	diff
expressionHeatmap	108	111	+3

ESLint disabled in files

id	before	after	diff
osquery	1	2	+1

ESLint disabled line counts

id	before	after	diff
enterpriseSearch	19	21	+2
fleet	57	63	+6
osquery	103	108	+5
securitySolution	439	445	+6
total			+19

Total ESLint disabled count

id	before	after	diff
enterpriseSearch	20	22	+2
fleet	65	71	+6
osquery	104	110	+6
securitySolution	516	522	+6
total			+20

History

• 💚 Build #84250 succeeded f5131e2
• 💚 Build #83605 succeeded 59b16b8

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

cc @Kunzetsov