Change lock type to RLock in metric_reader_storage

Replaced Lock with RLock for better handling of nested locks.

Author: dshivashankar1994

opentelemetry-sdk/src/opentelemetry/sdk/metrics/_internal/metric_reader_storage.py

@@ -77,7 +77,7 @@ def __init__(
 
     def _at_fork_reinit(self) -> None:
         """Reinitialize locks and clear state in the child process after fork."""
-        self._lock = Lock()
+        self._lock = RLock()
         self._instrument_view_instrument_matches.clear()
 
     def _get_or_init_view_instrument_match(