[7.x] [Fleet] add support for fleet server urls (#94364)

[kibanamachine]

Backports the following commits to 7.x:

• [Fleet] add support for fleet server urls ([Fleet] add support for fleet server urls #94364)

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: 4c9b9b5
• Storybooks Preview

Metrics [docs]

Module Count

Fewer modules leads to a faster build time

id	before	after	diff
fleet	461	462	+1

Async chunks

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

id	before	after	diff
fleet	705.7KB	716.3KB	+10.7KB

Saved Objects .kibana field count

Every field in each saved object type adds overhead to Elasticsearch. Kibana needs to keep the total field count below Elasticsearch's default limit of 1000 fields. Only specify field mappings for the fields you wish to search on or query. See https://www.elastic.co/guide/en/kibana/master/development-plugin-saved-objects.html#_mappings

id	before	after	diff
ingest_manager_settings	4	5	+1

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

cc @nchaulet