[Search][Discover] Send to background integration improvements and fixes

[Dosant]

Summary

Closes #87148

This pr makes couple improves to send to background integration in Discover:

1. Fixes discover URL generation in case there is a saved search. (Unfortunately to properly tests needs [Data/Search Sessions] Management UI #81707)
2. Uses saved search's name as search session name if available. Otherwise fallbacks to Discover (Unfortunately to properly tests needs [Data/Search Sessions] Management UI #81707. Also can be tested by inspecting network request that saves a session)
3. Moves discover session tests into separate test suite. This was done for dashboard tests in scope of [Send To Background UI] Isolate functional test for wip feature #84833 but we forgot to also move discover tests
4. Add a check in ftr that there is an error in case incorrect search session id is used during restoration

Checklist

• Unit or functional tests were updated or added to match the most common scenarios

[elasticmachine]

Pinging @elastic/kibana-app-services (Team:AppServices)

[lizozom]

Tested and LGTM, but please consider adding a timestamp to the session name.

[Dosant]

@elasticmachine merge upstream

[Dosant]

@elasticmachine merge upstream

[kertal]

ACK, will review

[kertal]

Code LGTM, was testing linking back via the management UI when you're using a saved search the link is correct, but there seems to be an error restoring the session, I think this is unrelated to this PR, so I'm approving this, maybe you could check before merging. many thx for the refactoring and adding tests

[Dosant]

@kertal, could this be related to the relative time range?
Support for restoring session with relative time range is not in master yet: #84405

[kertal]

@kertal, could this be related to the relative time range?
Support for restoring session with relative time range is not in master yet: #84405

oh, yes, thank, works with absolute time ranges :)

[kertal]

Code LGTM, tested locally, works with absolute time ranges, finally approving this, not pretending to do so :)

[Dosant]

@elasticmachine merge upstream

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: 17bcac9

Metrics [docs]

Async chunks

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

id	before	after	diff
discover	502.0KB	502.3KB	+312.0B

Page load bundle

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

id	before	after	diff
discover	81.7KB	81.7KB	+16.0B

History

• 💚 Build #98184 succeeded b88cac5
• 💚 Build #97833 succeeded 005ecef
• 💚 Build #97583 succeeded 1533590
• 💚 Build #96990 succeeded 7cf5182
• 💔 Build #96962 failed 806e714

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