storage controller: include stripe size in compute notifications

[jcsp]

Problem

• The storage controller is the source of truth for a tenant's stripe size, but doesn't currently have a way to propagate that to compute: we're just using the default stripe size everywhere.

Closes: #6903

Summary of changes

• Include stripe size in ComputeHookNotifyRequest
• Include stripe size in LocationConfigResponse

The stripe size is optional: it will only be advertised for multi-sharded tenants. This enables the controller to defer the choice of stripe size until we split a tenant for the first time.

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]

2490 tests run: 2366 passed, 0 failed, 124 skipped (full report)

---

Flaky tests (2)

Postgres 15

• test_empty_branch_remote_storage_upload: release

Postgres 14

• test_compute_pageserver_connection_stress: release

Code coverage* (full report)

• functions: 28.8% (6993 of 24258 functions)
• lines: 47.4% (43020 of 90680 lines)

* collected from Rust tests only

---

_{The comment gets automatically updated with the latest test results
4344e52 at 2024-03-06T11:36:49.914Z :recycle:}