Use OPENTELEMETRY_EXPORT for functions in meter_config & tracer_config

[psx95]

For meter_config and tracer_config, use OPENTELEMETRY_EXPORT to export all public static functions and default constructor, destructor and assignment operators.

Additionally use static local variables for default & disabled config objects to avoid unnecessary creation and ensure stable constructing and destructing order.

See reference in this issue comment for logger_config.

[psx95]

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