Bugfix and code cleanup for Ticket #1095.
Rate control in current VTM does not work. Issues are pointed out in Ticket #1095. This merge request is provided to fix them.
- Fix the wrong clipping of alpha and beta for intra frames.
- Fix the variable of number of CTUs left in rate allocation for intra frames.
- Fix the updating of alpha and beta for intra frames.
- Fix the missing chroma distortion weight for CTU level rate control.
- Code cleanup.