[Discover] Minimize references to DiscoverSavedSearchContainer

[davismcphee]

Summary

This PR minimizes many of the references to DiscoverSavedSearchContainer to get us closer to full removal. It's the first of two parts, and largely addresses these areas:

• Removes redundant DiscoverSavedSearchContainer methods for which there are equivalent alternatives, e.g. getId and getTitle.
• Lifts initUrlTracking directly into DiscoverStateContainer.initializeAndSync.
• Replaces various calls to searchSource.getField() with their Redux or runtime state equivalents.
• Migrates some functions that previously relied on SavedSearch to use DiscoverSessionTab or another equivalent, e.g. getInitialAppState.
• Updates several Jest test files to stop relying on SavedSearch and related mocks, using getDiscoverInternalStateMock instead.

Part of #241890.

Checklist

• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios
• If a plugin configuration key changed, check if it needs to be allowlisted in the cloud and added to the docker list
• This was checked for breaking HTTP API changes, and any breaking changes have been approved by the breaking-change committee. The release_note:breaking label should be applied in these situations.
• Flaky Test Runner was used on any tests changed
• The PR description includes the appropriate Release Notes section, and the correct release_note:* label is applied per the guidelines
• Review the backport guidelines and apply applicable backport:* labels.

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: 197f064

Metrics [docs]

Module Count

Fewer modules leads to a faster build time

id	before	after	diff
discover	1866	1865	-1

Async chunks

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

id	before	after	diff
discover	1.3MB	1.3MB	+410.0B

History

• 💔 Build #368790 failed 2084e7f
• 💚 Build #368768 succeeded 78da026
• 💚 Build #366886 succeeded 436e4bd

cc @davismcphee

[elasticmachine]

Pinging @elastic/kibana-data-discovery (Team:DataDiscovery)