Provide a common package for opentelemetry Instr.

[miyunari]

Description

Initializing the OpenTelemetry tracing SDK results in relatively boilerplate code to determine which propagator (which must be identical across all components) is used, etc.

Following #4101, I think it would be a good idea to provide a common package for the initialization, which can be used in e.g. Fulcio and Cosign.