[NFC][IntrRefLDV] Improve the Value printing

Basically, this just improves the dump of the Value stored within a location.

If the defining instruction number is zero, it means it is "live-in".

Before the patch:

ESI --> bb 0 inst 0 loc ESI
After:

ESI --> Value{bb: 0, inst: live-in, loc: ESI}
This is an NFC.

Differential Revision: https://reviews.llvm.org/D90309