pageserver: add gRPC authentication

[erikgrinaker]

Problem

We need authentication for the gRPC server.

Requires #11972.
Touches #11728.

Summary of changes

Add two request interceptors that decode the tenant/timeline/shard metadata and authenticate the JWT token against them.

[github-actions]

8492 tests run: 7945 passed, 0 failed, 547 skipped (full report)

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Flaky tests (5)

Postgres 17

• test_sharding_split_failures[failure10]: release-arm64-without-lfc
• test_storcon_create_delete_sk_down[DeletionSubject.TENANT-RestartStorcon.ONLINE]: release-arm64-without-lfc
• test_storcon_create_delete_sk_down[DeletionSubject.TENANT-RestartStorcon.RESTART]: release-arm64-without-lfc

Postgres 16

• test_sharding_split_failures[failure13]: release-arm64-with-lfc

Postgres 14

• test_pg_regress[v1-None]: release-arm64-with-lfc

Code coverage* (full report)

• functions: 32.4% (9051 of 27919 functions)
• lines: 48.7% (79449 of 163284 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
ad0ec36 at 2025-05-26T10:35:04.147Z :recycle:}