Print a log message if GetPage response takes too long

[hlinnaka]

We have metrics for GetPage request latencies, but this is an extra measure to capture requests that take way too long in the logs. The log message is printed every 10 s, until the response is received:

PG:2024-12-09 16:02:07.715 GMT [1782845] LOG:  [NEON_SMGR] [shard 0] no response received from pageserver for 10.000 s, still waiting (sent 10613 requests, received 10612 responses)
PG:2024-12-09 16:02:17.723 GMT [1782845] LOG:  [NEON_SMGR] [shard 0] no response received from pageserver for 20.008 s, still waiting (sent 10613 requests, received 10612 responses)
PG:2024-12-09 16:02:19.719 GMT [1782845] LOG:  [NEON_SMGR] [shard 0] received response from pageserver after 22.006 s

[hlinnaka]

We also talked about disconnecting and retrying with a new connection, if a request takes too long. I didn't dare to do that yet, but just logging long requests is useful already.

I set the threshold at 10 s, but I'm open to opinions on that. (A cop out answer would be to make it configurable, but I think that'd be overkill, and would still leave us with the question of what to actually set it to)

[github-actions]

7077 tests run: 6752 passed, 0 failed, 325 skipped (full report)

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Flaky tests (5)

Postgres 17

• test_idle_checkpoints: debug-x86-64
• test_pageserver_small_inmemory_layers[False]: debug-x86-64

Postgres 16

• test_prefetch[None]: release-arm64

Postgres 15

• test_prefetch[4]: release-arm64

Postgres 14

• test_pull_timeline[True]: release-arm64

Code coverage* (full report)

• functions: 31.4% (8333 of 26528 functions)
• lines: 47.7% (65568 of 137367 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
6af4747 at 2024-12-10T13:44:48.269Z :recycle:}