Update some flags in GLES_GPU.

It's useful to know if we need to have a correct PC value or downcount.
Merge pull request #5766 from unknownbrackets/gpu-minor

Update some flags in GLES_GPU
Fix performance issue in BlockCache due to an instance of std::vector in every block:

Avoid creating the vector when not necessary.

This was especially noticeable in debug mode.
Reduce some includes under GPU/.
Include sceKernelThread.h in less headers.
Avoid a crash with a huge user memory font size.

Fixes tests.
Add some basic bounds checking for power freq sets.