Upload Test Remote Extensions

[awestover]

Problem

We need some real extensions in S3 to accurately test the code for handling remote extensions.
In this PR we just upload two extensions (anon and kq_imcx), which is enough for testing purposes for now. In addition to creating and uploading the extension archives, we must generate a file ext_index.json which specifies important metadata about the extensions. See below.

Summary of Changes

The layout of the S3 bucket is as follows:

5615610098 // this is an extension build number
├── v14
│   ├── extensions
│   │   ├── anon.tar.zst
│   │   └── embedding.tar.zst
│   └── ext_index.json
└── v15
    ├── extensions
    │   ├── anon.tar.zst
    │   └── embedding.tar.zst
    └── ext_index.json
5615261079
├── v14
│   ├── extensions
│   │   └── anon.tar.zst
│   └── ext_index.json
└── v15
    ├── extensions
    │   └── anon.tar.zst
    └── ext_index.json
5623261088
├── v14
│   ├── extensions
│   │   └── embedding.tar.zst
│   └── ext_index.json
└── v15
    ├── extensions
    │   └── embedding.tar.zst
    └── ext_index.json

ext_index.json stores the control files and location of extension archives.

More specifically, here is an example ext_index.json

{
  "embedding": {
    "control_data": {
      "embedding.control": "comment = 'hnsw index' \ndefault_version = '0.1.0' \nmodule_pathname = '$libdir/embedding' \nrelocatable = true \ntrusted = true"
    },
    "archive_path": "5623261088/v15/extensions/embedding.tar.zst"
  },
  "anon": {
    "control_data": {
      "anon.control": "# PostgreSQL Anonymizer (anon) extension \ncomment = 'Data anonymization tools' \ndefault_version = '1.1.0' \ndirectory='extension/anon' \nrelocatable = false \nrequires = 'pgcrypto' \nsuperuser = false \nmodule_pathname = '$libdir/anon' \ntrusted = true \n"
    },
    "archive_path": "5615261079/v15/extensions/anon.tar.zst"
  }
}

[awestover]

Note: this is safe to merge, it has already been tested in #4764
This is just a squashed version of #4764 . I made it primarily because I didn't want to mess up the git history on @bayandin 's branch

[github-actions]

1240 tests run: 1187 passed, 0 failed, 53 skipped (full report)

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Flaky tests (1)

Postgres 15

• test_metrics_normal_work: release