[processor/tailsamplingprocessor] Deprecate sampled attribute

[yvrhdn]

Description

This is a follow-up task from #41819: deprecate the sampled attribute on metrics which have decision.

Queries using sampled can be updated:

• sampled="true" ➡️ decision="sampled"
• sampled="false" ➡️ either decision!="sampled" or decision=~"not_sampled|dropped"

This impacts the following metrics

otelcol_processor_tail_sampling_count_traces_sampled
otelcol_processor_tail_sampling_count_spans_sampled
otelcol_processor_tail_sampling_global_count_traces_sampled

This does not impact

otelcol_processor_tail_sampling_early_releases_from_cache_decision

Since this metric doesn't have decision. (When we make a sampling decision based upon the cache, we don't have enough context to fill in the decision).

[yvrhdn]

@atoulme can you take a look again please? I got a review from the code owner so I believe this PR is good to go 🙂

[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 14 days.

[yvrhdn]

This PR is not stale! It should be all good to get merged

[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 14 days.