DenseSet, SmallPtrSet, SmallSet, SetVector, and StringSet recently
gained C++23-style insert_range.  This patch replaces:

  Dest.insert(Src.begin(), Src.end());

with:

  Dest.insert_range(Src);

This patch does not touch custom begin like succ_begin for now.

When a def in a block A reaches another block B that is in A's iterated
dominance frontier, a phi node is added to B for the def register.

A clobbering def can be created at a call instruction, for a register
clobbered by a call.
However, phi nodes are not created for a register, when one of the
reaching defs of the register is a clobbering def.

This patch adds phi nodes for registers that have a clobbering reaching
def. These additional phis help in checking reaching defs for an
instruction in RDF based copy propagation and addressing mode
optimizations.

During RDF graph construction, linkRefUp method links a register ref to
its upward reaching defs until all RegUnits of the ref have been covered
by defs.
However, when a sub-register def covers some, but not all, of the
RegUnits of a previous super-register def, a super-register ref is not
linked to the super-register def.
This can result in certain super register defs being dead code
eliminated.

This patch fixes the cover check for a register ref. A def must be
skipped only when all RegUnits of that def have already been covered by
a previously seen def.

Identified with misc-include-cleaner.

MachineRegisterInfo::liveins returns std::pair<MCRegister, Register>.
Don't convert to std::pair<unsigned, unsigned>.

Closes #89198

This just avoids useless work of adding NoRegister to BaseSet, for
consistency with other places that iterate over all physical registers.

- Add option to ignore reserved registers
- Add possibility to track selected registers or register classes only

Tracking is done based on register units, so the set of registers to track
is translated into a set of register units.