chore(integration-tests): improve error logging for better debugging

[jchrostek-dd]

Summary

• Integration tests can sometimes be a little flaky. It isn't clear what the errors are, but seems like some sort of request throttling. Rerunning the tests succeeds. Adding some better logging for this.
• No changes to actual extension code.

Changes

• invoke.ts: Log TooManyRequestsException reason and retryAfterSeconds
• lambda.ts: Add detailed error logging to publishVersion(), setTimestampEnvVar(), waitForSnapStartReady()
• datadog.ts: Log HTTP status, rate limit headers, and query context for API errors
• misc: Moved lambda invoke code from invoke.ts to lambda.ts.

Example Output

Lambda invocation failed for 'my-function': TooManyRequestsException - Rate exceeded - (Reason: ConcurrentSnapshotCreateLimitExceeded) - (retryAfterSeconds: 5)
Error searching traces: Error (query: 'service:my-service @request_id:abc123'): HTTP 429 Too Many Requests (retry-after: 30s)

Test plan

• TypeScript build passes
• Manual verification during next integration test run

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