Add GRAPHICS_PIPELINE session mode

This patch adds a new performance hint session mode,
GRAPHICS_PIPELINE, indicating that the threads associated with
this hint session is of graphics pipeline, namely on critical path.

This session mode allows HAL to know that these threads are of higher
priority and can schedule CPU resources accordingly.

Bug: 362801903
Bug: 367803904
Test: atest HintManagerServiceTest
      atest PerformanceHintNativeTest
Flag: EXEMPT_NDK
Change-Id: I164b2e29de79bbe27c14358924cb421457831325