Fix CFI issues with extractor threading

Recent changes in libutils exposed some issues where a library was
linked both static and shared into the extractor. This caused CFI
crashes in the extractor during DRM MediaCas processing.

The plugin where this triggered has been modified to (1) use the shared
library instance and (2) change from Mutex to std::mutex to reduce
dependency on that code.

Bug: 379803959
Test: CtsMediaDrmFrameworkTestCases:android.media.drmframework.cts.MediaDrmClearkeyTest
Flag: EXEMPT bugfix
Change-Id: I5ea5337b2b8816f64f5a28b7b144d710fc2f8123