RA-7777: [Trillian] Added event timing that conforms to opentelemetry standards.

[himaschal]

Changes made:

This PR introduces basic OpenTelemetry-style trace and span ID propagation and structured logging middleware to the Trillian server. The changes are focused on improving observability and request tracing for both HTTP and gRPC endpoints.

• Added request tracing - with a focus on timing - to Trillian log server which allows for structured logging of a request from http through to the gRpc calls.
• Added structured logging package with transaction and span ID tracking
• HTTP middleware for automatic request timing and context injection
• gRPC interceptor for consistent tracing across service boundaries
• Context propagation between HTTP and gRPC calls using standardized headers
• JSON logging format
• Added / updated tests
• The logging is handled by the logrus library - which is useful for structured output.
• Conforms to the opentelemetry standards for request correlation id's etc.

The are 2 health endpoints exposed in terms of the trillian project:

• /metrics which uses the prometheus http handler and by default are not logged (this is standard practice) ie. we will not see any logs for this
• /healthz which uses the standard http handler, runs on schedule, and we will see logs for these

{"elapsed":"0ms","event_id":"timing","level":"info","method":"GET","msg":"request completed","path":"/healthz","span_id":"e52096a54fe76c74","status":200,"time":"2025-07-30T08:03:39.413Z","trace_id":"26870f0e8feb8c310f1b327e9740d282"}
{"elapsed":"0ms","event_id":"timing","level":"info","method":"GET","msg":"request completed","path":"/healthz","span_id":"4955ed2f3c011b0e","status":200,"time":"2025-07-30T08:04:09.413Z","trace_id":"6ac1f80f10b665da523e5ac0fb0f0018"}
{"elapsed":"0ms","event_id":"timing","level":"info","method":"GET","msg":"request completed","path":"/healthz","span_id":"3da73e7ec906d795","status":200,"time":"2025-07-30T08:04:39.412Z","trace_id":"82b811e0a0bded795379b0b173b4a478"}
{"elapsed":"0ms","event_id":"timing","level":"info","method":"GET","msg":"request completed","path":"/healthz","span_id":"dfc9cdddae887aaf","status":200,"time":"2025-07-30T08:05:09.410Z","trace_id":"c4d03a16c17588e50f53a22c6c4197a0"}
{"elapsed":"1ms","event_id":"timing","level":"info","method":"GET","msg":"request completed","path":"/healthz","span_id":"1f22ec8af0ea9848","status":200,"time":"2025-07-30T08:05:39.411Z","trace_id":"03706449e94d468fdaebb7f203acf5d1"}
{"elapsed":"0ms","event_id":"timing","level":"info","method":"GET","msg":"request completed","path":"/healthz","span_id":"e956b94da9578b2f","status":200,"time":"2025-07-30T08:06:09.413Z","trace_id":"6164ac16d5df1f7bce54f26eea05064c"}

We can also see that the gRpc call is logged (tested from invoking the get-sth call and tracing through)

curl -H 'traceparent: 00-$(openssl rand -hex 16)-$(openssl rand -hex 8)-01' http://localhost:6962/log/ct/v1/get-sth
Handling connection for 6962
{"tree_size":0,"timestamp":1753850472067,"sha256_root_hash":"47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU=","tree_head_signature":"BAMASDBGAiEAvDCfQQenVkH7s4zI+Nw5Ueugok7ntLsTCoZ5lN8ZaWsCIQCAAV2jofjsu0uEyCNr6YwsXzgXJ/tVihO57ORIqZLfKw=="}%

Expected:
Both the CTFE and Logserver should have the same trace_id and different span id's

CTFE logs:

{"elapsed":"3ms","event_id":"timing","level":"info","method":"GET","msg":"request completed","path":"/log/ct/v1/get-sth","span_id":"613cf118eb34bf77","status":200,"time":"2025-07-30T08:13:05.593Z","trace_id":"5e7facbbfcd4725608bde5bac22f2606"}

Logserver (Trillian):

{"elapsed":0,"event_id":"timing","level":"info","method":"/trillian.TrillianLog/GetLatestSignedLogRoot","msg":"gRPC call completed","span_id":"87be766ec02e7cef","status":"OK","time":"2025-07-30T08:13:05.592Z","trace_id":"5e7facbbfcd4725608bde5bac22f2606"}

[ryanmilne-digicert]

change this to just .DS_Store and it will exclude it from all folders.