fix: allow OTLP allocation and lock thresholds

[arnabnandy7]

Description

Allows OTLP export to use allocation and lock profiling thresholds when the threshold configures the selected primary event.

Valid configurations now include:

PYROSCOPE_FORMAT=otlp
PYROSCOPE_PROFILER_EVENT=alloc
PYROSCOPE_PROFILER_ALLOC=512k

and:

PYROSCOPE_FORMAT=otlp
PYROSCOPE_PROFILER_EVENT=lock
PYROSCOPE_PROFILER_LOCK=10ms

Previously, any use of PYROSCOPE_PROFILER_ALLOC or PYROSCOPE_PROFILER_LOCK with OTLP was rejected, even though async-profiler treats these values as thresholds for the selected event.

The validation still rejects distinct events running simultaneously. Multiple events remain supported in sampling mode, where they run sequentially.

Changes

• Allow allocation thresholds when alloc is the primary event.
• Allow lock thresholds when lock is the primary event.
• Preserve validation against simultaneous OTLP profiling events.
• Add coverage for allocation, lock, invalid simultaneous events, and sequential sampling.
• Document the supported OTLP configurations.

Testing

./gradlew :agent:test --tests io.pyroscope.javaagent.config.OtlpConfigTest

Fixes #347

[arnabnandy7]

@korniltsev-grafanista to review

[korniltsev-grafanista]

do not update readme. The information here is quickly outdated. The documentation lives in grafana/pyroscope repo.