[processor/probabilisticsampler] add more mterics to probabilistic sampler

[JaredTan95]

Is your feature request related to a problem? Please describe.
wish to expose more metrics to observe probabilistic processor stats.

Describe the solution you'd like
following https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/processor/tailsamplingprocessor/metrics.go#L47

I'd like to add those. pls assign it to me. :-P

[github-actions]

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