Remove redundant zero-initialization of struct temps with GC fields. (#13868)

Remove redundant  zero-initialization of struct temps with GC fields. (#13868)

Remove redundant  zero-initialization of struct temps with GC fields.

Structs with GC pointer fields are fully zero-initialized in the prolog if compInitMem is true.
Therefore, we don't need to insert zero-initialization for the result of newobj or for inlinee locals
when they are structs with GC pointer fields and the basic bock is not in a loop.