Rename options named tracing that do logging

Googlers can see: go/cloud-cxx:s-slash-tracing-logging-options

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I say we adopt OpenTelemetry’s naming scheme for our telemetry interfaces. This basically means s/Tracing/Logging/ for these types.

We will introduce new types using “Logging” instead of “Tracing”. We will leave using declarations for the old types, for backwards compatibility. We will also mark the old types as deprecated.

This looks like:
- introducing `g::c::LoggingComponentsOption`, to replace `g::c::TracingComponentsOption`.
- introducing `g::c::LoggingFormat`, to replace g::c::TracingOptions.
- introducing `g::c::LoggingFormatOption`, (in common) to replace `g::c::GrpcTracingOptionsOption` and `g::c::RestTracingOptionsOption`.
- introducing `GOOGLE_CLOUD_CPP_ENABLE_LOGGING`, `GOOGLE_CLOUD_CPP_LOGGING_FORMAT` to replace the old ones. We still respect the legacy environment variables for backwards compatibility, but we purge our docs of them.

We will need to do a pass on the public docs referencing the old types / old env vars.

We also need to look into legacy GCS env var: `CLOUD_STORAGE_TRACING`

Start by searching the public API declarations and documentation for the listed Tracing types, environment variables, and the legacy CLOUD_STORAGE_TRACING name. Trace each reference before planning the rename, then verify that the new Logging names are documented while legacy names and variables remain supported and deprecated as specified.

Vom Indexierungsmodell aus dem Issue-Text verfasst.