Spec tracking: Support LoggerConfigurator

[dashpole]

The specification defines a LoggerConfigurator function which computes the LoggerConfig for a Logger.

LoggerConfigurator is currently experimental, and must not be exposed as part of the public API of the log or sdk/log 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 LoggerConfigurator:

• https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/logs/sdk.md#logger-creation
• https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/logs/sdk.md#loggerconfigurator

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