refactor: cache protobuf parser method lookup

Motivation:
Address PR review feedback that repeatedly calling MethodHandles.publicLookup() has unnecessary overhead while keeping the MethodHandle-based parser resolution behavior.

Modification:
Store a shared public Lookup for Java protobuf parser discovery and cache parser MethodHandles with a ConcurrentHashMap putIfAbsent pattern to avoid non-atomic TrieMap getOrElseUpdate lookup races.

Result:
ProtoAnySerialization reuses the public lookup and aligns parser handle caching with the existing ConsumerFilterStore MethodHandle cache style.

Tests:
- scalafmt --mode diff-ref=origin/main
- scalafmt --list --mode diff-ref=origin/main
- sbt "grpc-test / Test / testOnly org.apache.pekko.projection.grpc.internal.ProtoAnySerializationSpec"
- sbt "jdbc / Test / testOnly org.apache.pekko.projection.jdbc.JdbcProjectionTest org.apache.pekko.projection.jdbc.JdbcOffsetStoreSpec"
- sbt "jdbc / Test / testOnly org.apache.pekko.projection.jdbc.H2JdbcOffsetStoreSpec"
- sbt "jdbc-int-test / Test / testOnly org.apache.pekko.projection.jdbc.JdbcProjectionSpec"
- sbt "examples / Test / compile"
- git diff --check
- qodercli stdout review: No must-fix findings (/tmp/project-qoder-review-2.log)

References:
Refs apache/pekko-projection#561