Error fix from enabling Clang thread-safety checks

Parent bug: b/353324127. Enabling `thread-safety-reference-return`
to allow developers to utilize Clang thread safety guardrails
(GUARDED_BY, REQUIRES, EXCLUDES).

Added NO_THREAD_SAFETY_ANALYSIS annotations to violating functions.
If this is not desired, please respond with concerns
or preferred fix.

Bug: 354740314
Test: m  libsurfaceflinger_unittest
Change-Id: I590ab37c7abe727ab827a99d2917dd15b534e1cf

Author: eprucka3

services/surfaceflinger/tests/unittests/FrameTimelineTest.cpp

@@ -158,6 +158,7 @@ class FrameTimelineTest : public testing::Test {
                 a.presentTime == b.presentTime;
     }
 
+    NO_THREAD_SAFETY_ANALYSIS
     const std::map<int64_t, TimelineItem>& getPredictions() const {
         return mTokenManager->mPredictions;
     }