[HTTP] Log build number mismatch

[jloleysens]

This PR adds new behaviour to log a message when we are not enforcing strict client-server build number checks and see a different build number.

How to test

• Start Kibana
• Set server.versioned.strictClientVersionCheck: false in kibana.dev.yml
• Send a request that will return a bad response, in my case I sent POST /api/files/files/defaultImage with an empty body {}

Assumptions

• We only want to log when we are returning a bad response (>=400). It's possible that we miss events this way, but the assumption is that status codes >=400 are a strong indication that something is wrong, i.e. we don't care about mismatches when good responses happen
• We want to treat this as a WARN level log
• We will be able to track this in o11y using the logger context (like kbn-build-number-mismatch)

Example

[2023-11-02T13:52:48.134+01:00][WARN ][http.kbn-build-number-mismatch] Client build (999999) is older than this Kibana server build (9007199254740991). The [400] error status in req id [29ad1f7c-056a-419b-9051-b45598aebd2c] may be due to client-server incompatibility!

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: 986700f

Metrics [docs]

✅ unchanged

History

• 💔 Build #172750 failed e428360
• 💔 Build #172486 failed 314bf35
• 💔 Build #172481 failed 952f3e0
• 💔 Build #172328 failed fad5a15

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@elasticmachine merge upstream