Spec Tracking: TracerConfigurator and TracerConfig

[dashpole]

The specification defines a TracerConfigurator function which computes the TracerConfig for a Tracer.

TracerConfigurator is currently experimental, and must not be exposed as part of the public API of the trace or sdk/trace packages if implemented. Prior to opening a PR, this issue must have an approved implementation plan, posted as a comment by the assignee, and signed off by a maintainer.

The following links include the specifications related to TracerConfigurator:

• https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/sdk.md#tracer-creation
• https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/sdk.md#configuration
• https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/sdk.md#tracerconfigurator
• https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/sdk.md#tracer
• https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/sdk.md#tracerconfig

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