In the method MetalContext.clearRtt,
- For clearing the whole rtt we depend on LoadAction of RenderEncoder.
- That requires to end the ongoig Encoder and create a new RenderEcoder
- The LoadAction itself is good idea to clear but ending the encoder here does not allow to merge any other encoders that qualify merge criteria.

We tried a change for this,
- It works correctly on intel mac, and shows a gain of 2-3 FPS in blend samples
- But, It shows rendering artifacts on M1, which must be a scenario of stricter state management on M1 than intel mac.