Implement part of the tracing SDK spec to configure the tracers
https://opentelemetry.io/docs/specs/otel/trace/sdk/#configuration

At the moment this adds helper in order to enable or disable a tracer
after it has been created.

The spec in is development so attributes, helpers and classes are
prefixed with underscore.

TODO: hook into sdk configuration

…eclarative config schema

So instead of caching it when the TracerConfigurator changes calculate
it when we need to check if the tracer is enabled. This simplify the
code quite a bit and hopefully people will use fast tracer configurator.

* opentelemetry-sdk: Implement tracer configurator

Implement part of the tracing SDK spec to configure the tracers
https://opentelemetry.io/docs/specs/otel/trace/sdk/#configuration

At the moment this adds helper in order to enable or disable a tracer
after it has been created.

The spec in is development so attributes, helpers and classes are
prefixed with underscore.

TODO: hook into sdk configuration

* Please lint

* Add rule based tracer configurator

* Assume rule based tracer configurator in helpers

* Fix lint

* Add changelog

* hook into auto-instrumentation

* Don't return invalid spans from NoOpTracer

* Adapt after nooptracer behaviour change

* Please lint

* Rework _RuleBasedTracerConfigurator interface to match the one from declarative config schema

* More correct nooptracer and more test coverage

* Ignore typechecking in validation test

* Handle invalid span context more gracefully

* Return invalid span in case span context is invalid

* Use tuple for typing

* Add retries in case of failure in copying the cached tracers

* Calculate the TracerConfig in start_span

So instead of caching it when the TracerConfigurator changes calculate
it when we need to check if the tracer is enabled. This simplify the
code quite a bit and hopefully people will use fast tracer configurator.

* Make Tracer.is_enabled a method since it does some computation

* Add benchmarks

* Test also the case with no overhead

* Use functools.lru_cache to recover the overhead of tracerConfigurator

* Fix pylint

* Fix precommit

* Make scope matcher generic per Lukas suggestion