Adding a dynamic_branch directive reduces CPU performance

STR:
1. Open the attached project
2. Open SampleScene
3. Enter play mode, enable stats window, check frame time
4. Add `#pragma dynamic_branch FOO BAR` to the `Test` shader.
5. Enter play mode, check frame time

Expected: frame time difference is minimal (<= 0.1ms)
Actual: frame time differs by more than 0.1ms (0.5ms+ on MBP M1 Max)