Add per-property has<Prop>/set<Prop>/reset<Prop> functions to
MachineFunctionProperties.

We previously had a heuristic that if a value V was used multiple times
in a single PHI, then to avoid potentially rematerializing into many predecessors
we bail out. The phi uses only counted as a single use in the shouldLocalize() hook
because it counted the PHI as a single instruction use, not factoring in it may
have many incoming edges.

It turns out this heuristic is slightly too pessimistic, and allowing a small number
of these uses to be localized can improve code size due to shortening live ranges,
especially if those ranges span a call.

This change results in some improvements in size on CTMark -Os:
```
Program                                       size.__text
                                              before         after           diff
kimwitu++/kc                                  451676.00      451860.00       0.0%
mafft/pairlocalalign                          241460.00      241540.00       0.0%
tramp3d-v4/tramp3d-v4                         389216.00      389208.00      -0.0%
7zip/7zip-benchmark                           587528.00      587464.00      -0.0%
Bullet/bullet                                 457424.00      457348.00      -0.0%
consumer-typeset/consumer-typeset             405472.00      405376.00      -0.0%
SPASS/SPASS                                   410288.00      410120.00      -0.0%
lencod/lencod                                 426396.00      426108.00      -0.1%
ClamAV/clamscan                               380108.00      379756.00      -0.1%
sqlite3/sqlite3                               283664.00      283372.00      -0.1%
                           Geomean difference                               -0.0%
```
I experimented with different variations and thresholds. Using 3 instead
of 2 resulted in a further 0.1% improvement on ClamAV but also regressed
sqlite3 by the same %.

This is a helper function to very slightly simplify many calls to
MachineInstruction::getOperandNo.

Differential Revision: https://reviews.llvm.org/D143250

After IRTranslator pass, constants are deduplicated and translated into instructions at entry block, having debug locations lost.
Localization of constants may cause emission of extra zero lines in debug_line section, like here https://godbolt.org/z/ecvsxxfKn. In this example, constant gets placed as
a first instruction in entry block, and despite it has no debug location, AsmPrinter emits zero line for it.

If a localized constant has the only user, we can assume that it has the same debug location as its user, since they are placed consequently.

Differential Revision: https://reviews.llvm.org/D128192

Discourse thread: https://discourse.llvm.org/t/include-what-you-use-include-cleanup
Differential Revision: https://reviews.llvm.org/D121332

This was inserting the new G_CONSTANT after the use, and the later
block scan would run off the end. Fix calling SkipPHIsAndLabels for no
apparent reason.