[ML] Functional tests - stabilize and re-enable test suites

[pheyos]

Summary

This PR stabilizes and re-enables a few ML functional test suites.

Details

Re-enable pages test suite

Test ran into a blank page with [SEVERE] http://localhost:5620/57029/bundles/kbn-ui-shared-deps-npm/kbn-ui-shared-deps-npm.dll.js 398:83112 TypeError: Reduce of empty array with no initial value. Seems to be resolved now.
Closes #142397

Stabilize and re-enable lens-to-ml test suites

There was an issue with test cleanups, which could bring up confusing failure messages in follow-up tests. The stability fix is to move the job deletion to an after method. The root cause of the issue seems to be resolved already.
Closes #144186
Closes #142762

Stabilize and re-enable index data visualizer test suite

With the introduction of random sampler in the data visualizer, the total document count was sometimes not the accurate value. The stability fix is to disable random sampling for this assertion by default.
Closes #143007

Stabilize and re-enable custom URL test suite

After navigating to Discover, the test sometimes failed to close the Discover side bar when clicking it too early after navigating to the page. The stability fix is to wait for global loading to finish before closing the side bar.
Closes #143933

[pheyos]

Checking test stability in a flaky test runner job ... no ML failure in 50 runs ✔️
(just one unrelated infrastructure issue that passed on 2nd try).

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: 13fc2da

Metrics [docs]

Unknown metric groups

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	59	65	+6
osquery	108	113	+5
securitySolution	440	446	+6
total			+19

Total ESLint disabled count

id	before	after	diff
enterpriseSearch	20	22	+2
fleet	67	73	+6
osquery	109	115	+6
securitySolution	517	523	+6
total			+20

History

• 💔 Build #86219 failed 832f93f
• 💚 Build #86126 succeeded e1734ed

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

[elasticmachine]

Pinging @elastic/ml-ui (:ml)

[qn895]

LGTM 🎉

[kibanamachine]

💔 All backports failed

Status	Branch	Result
❌	8.5	Backport failed because of merge conflicts You might need to backport the following PRs to 8.5: - [ML] Add functional tests for Index data visualizer's random sampler controls (#142278)

Manual backport

To create the backport manually run:

node scripts/backport --pr 144784

Questions ?

Please refer to the Backport tool documentation