Clear *_ASG_LHS flags in ResetOptAnnotations

Clear *_ASG_LHS flags in ResetOptAnnotations

This works around an apparent bug in SSA construction (GitHub issue #7846),
specifically `fgPerNodeLocalVarLiveness`, where heap uses are not
considered upwards-exposed if they follow a heap def in their block (which
is incorrect because the store and load are not necessarily must-alias).
In the non-repeat configuration, these flags are always cleared coming
into SSA construction, because `TreeRenameVariables` is the only thing
that sets them.