chore(proxy): remove code for old API

[conradludgate]

Problem

Now that https://github.com/neondatabase/cloud/issues/15245 is done, we can remove the old code.

Summary of changes

Removes support for the ManagementV2 API, in favour of the ProxyV1 API.

[awarus]

Great, thanks!

By the way, is it fine to merge it before removing old proxy tests from the cloud, or should we remove them there first?

[conradludgate]

All tests should be directly interfacing with cplane, or going via proxy that you've already changed to point to proxyv1 api, so I think this should be fine? We can remove the endpoints from cplane at a later time.

[cloneable]

LGTM. Not sure why the new auth method already needs an alias.

[github-actions]

7740 tests run: 7409 passed, 0 failed, 331 skipped (full report)

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Flaky tests (3)

Postgres 16

• test_pageserver_gc_compaction_smoke: release-x86-64

Postgres 15

• test_scrubber_physical_gc_ancestors[None]: release-arm64
• test_timeline_archive[4]: release-arm64

Code coverage* (full report)

• functions: 31.4% (8374 of 26700 functions)
• lines: 47.8% (65912 of 137916 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
aa439cd at 2024-12-12T11:55:26.176Z :recycle:}