Support gRPC 1.82 and fix test parallelism

[tm-drtina]

Summary

Update tests to work with gRPC 1.82+, which enables the error_flatten experiment
that drops status messages for OK status (matching absl::Status semantics).
Also fix test failures caused by Tasty 1.5.4 enabling parallel execution by default.

Changes

gRPC 1.82 compatibility

• Expose grpcCppVersionMajor / grpcCppVersionMinor from Network.GRPC.Unsafe
  via C helpers that read GRPC_CPP_VERSION_MAJOR / GRPC_CPP_VERSION_MINOR
  from grpcpp/version_info.h (since grpc_version_string() returns the
  internal core version, not the release version)
• Use runtime version check in core tests to conditionally expect empty status
  details for OK responses on gRPC >= 1.82

Test parallelism fixes

• Tasty 1.5.4 makes -j entail +RTS -N automatically, which causes tests
  to run in parallel by default
• grpc-haskell-core: Set NumThreads 1 since all network tests share port 50051
• grpc-haskell: Wrap generated code tests in dependentTestGroup AllFinish
  since they share port 50051 and temp directory tests/tmp