[Search Sessions][Dashboard] Clear search session when navigating from dashboard route

[Dosant]

Summary

Currently dashboard calls session.clear() only when dashboard app is unmounted:
https://github.com/elastic/kibana/blob/master/src/plugins/dashboard/public/application/dashboard_router.tsx#L222

The session isn't clear when navigating within the dashboard app which leads to a stale session indicator:

This pr adds session.clear() when dashboard app route unmounts.
I also had to leave the original clear because of #82877

Checklist

Delete any items that are not applicable to this PR.

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

For maintainers

• This was checked for breaking API changes and was labeled appropriately

[ThomThomson]

Code only review, but change LGTM. Good to add a functional test for it as well!

[Dosant]

@elasticmachine merge upstream

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: 4808729

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
dashboard	160.7KB	160.9KB	+112.0B

History

• 💚 Build #102201 succeeded 78eeff0

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