fix reshaper interaction with IBC, and, modify encoder CW allocation constraint to avoid potential out-of-bound array access in ReverseLUT()

First aspect: the old IBC implementation change I slice type to P for intra slice. For class F LDP coding condition, both inter slice and intra slice will have P slicetype. When coding inter slices, this results in entering wrong encoder rocess for intra slice reshaping. After new IBC change, intra slicetype is not changed anymore. Condition checks for reshaping has been modified accordingly to fix the issue.

Second aspect: modify encoder CW allocation constraint (max allowed CW is 1023 instead of 1024) to avoid potential out-of-bound array access in ReverseLUT().