[8.12] [Obs AI Assistant] Fall back to request.url for kibana fn (#173717)

[kibanamachine]

Backport

This will backport the following commits from main to 8.12:

• [Obs AI Assistant] Fall back to request.url for kibana fn (#173717)

Questions ?

Please refer to the Backport tool documentation

[kibana-ci]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: 76995c4

Failed CI Steps

• FTR Configs #9

Test Failures

• [job] [logs] FTR Configs #9 / spaces api with security get all rbac user with read globally can access all spaces from default undefined purpose should return 200 when referencing the default space implicitly

Metrics [docs]

✅ unchanged

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

cc @dgieselaar