Wrong accumulation of cost information in local dual tree

[lzz8246]

Local dual tree is proposed to disallow chroma intra CBs smaller than TH samples by constraining the partitioning of Chroma intra CBs. In current implementation，the function useSubStructure is called to copy temp chroma information into a global CS when local dual tree is used. However, the function "useSubSturcture()" is designed to converge information of different sub structures, which means that besides block copy, useSubstructure is also used to accumulate cost information, i.e., fracBits, dist, cost and costDbOffset. It leads to incorrect result of cost information in global CS during the iteration of "xCheckModeSplit()". Currently, no mudule in CTC uses these cost information, hence this bug does not cause performance loss. However, non-CTC tools might use these info, e.g., rate control. Therefore, we have submitted MR !XXX to fix it in this ticket. Noting that the performance of CTC is not influenced by this bugfix.

[lzz8246]

The MR number is !1612.

[XiangLi]

Fixed in ​https://vcgit.hhi.fraunhofer.de/jvet/VVCSoftware_VTM/-/merge_requests/1612.