Debug Logging improvements

[bshaffer]

A few things to keep track of for improving Debug Logging for next year:

• Remove logging of client configuration when OperationsClient is created by GAPIC clients (this is a tricky issue that will require some consideration)
• Create a standalone logging library (e.g. StructuredLoggingEvent or something similar) based on https://cloud.google.com/logging/docs/structured-logging
• Test the logging in GrpcFallbackTransport
• Consider logging Response Status Code ONLY when logger level is set to INFO
• Add back readonly to RpcLogEvent::$timestamp and RpcLogEvent::$milliseconds once we drop support for PHP 8.0
• Add a static method to get the requestId instead of repeating "crc32((string) spl_object_id($request) . getmypid())" every time.
  • NOTE: There are some places which use the requestID, like RestTransport, which do not implement LoggingTrait, and so if we wanted one place for it to be generated, we would need a static method somewhere instead. Could be a private method like LoggingTrait::getRequestId, or a public static method such as RpcLogEvent::getRequestId($request).
• Verify what types of requests/responses ClientStream/BidiStream can accept and potentially tighten the typing and/or log them (right now it only logs requests of type Message)
• Look into why REST JSON responses contain newlines (might be in Guzzle), and if we can strip them.