[processor/tailsamplingprocessor] move it to a stable component

[alexfdz]

Is your feature request related to a problem? Please describe.
tailsamplingprocessor has been in beta for a while, is there any issue or missing feature we can help with?

It probably won't be included in distributions like aws-otel-collector if is not considered stable.

Describe the solution you'd like
tailsamplingprocessor to be considered a stable component.

Describe alternatives you've considered

Additional context
Probably related to #1797

[djaglowski]

cc: @jpkrohling as code owner

[jpkrohling]

I'm aware of a potential minimal leak I found while putting this under extreme pressure. Unfortunately, I wasn't able to find the cause of this potential leak. Despite that, I think we can indeed move it to stable, as I'm aware of people using it in production and haven't experienced this potential problem.

[jpkrohling]

We are currently having discussions on what it means to be "stable". Given that "stable" might mean strict rules on the configuration properties, we might not want to move this to stable.

[jpkrohling]

I'm closing this as I don't think we are ready to declare this stable.