[TwoAddressInstructionPass] Put all new instructions into DistanceMap

In function convertInstTo3Addr, after converting a two address instruction into
three address instruction, only the last new instruction is inserted into
DistanceMap. This is wrong, DistanceMap should track all instructions from the
beginning of current MBB to the working instruction. When a two address
instruction is converted to three address instruction, multiple instructions may
be generated (usually an extra COPY is generated), all of them should be
inserted into DistanceMap.

Similarly when unfolding memory operand in function tryInstructionTransform
DistanceMap is not maintained correctly.

Differential Revision: https://reviews.llvm.org/D111857