Rename options named tracing that do logging

[dbolduc]

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