pageserver: remove tenant create API

[jcsp]

Problem

For some time, we have created tenants with calls to location_conf. The legacy "POST /v1/tenant" path was only used in some tests.

Summary of changes

• Remove the API
• Relocate TenantCreateRequest to the controller API file (this used to be used in both pageserver and controller APIs)
• Rewrite tenant_create test helper to use location_config API, as control plane and storage controller do
• Update docker-compose test script to create tenants with location_config API (this small commit is also present in pageserver: remove legacy tenant config code, clean up redundant generation none/broken usages #7947)

Checklist before requesting a review

• I have performed a self-review of my code.
• If it is a core feature, I have added thorough tests.
• Do we need to implement analytics? if so did you add the relevant metrics to the dashboard?
• If this PR requires public announcement, mark it with /release-notes label and add several sentences in this section.

Checklist before merging

• Do not forget to reformat commit message to not include the above checklist

[github-actions]

2934 tests run: 2817 passed, 0 failed, 117 skipped (full report)

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Code coverage* (full report)

• functions: 32.7% (6894 of 21102 functions)
• lines: 50.0% (53912 of 107846 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
40847ed at 2024-06-26T19:33:06.400Z :recycle:}