This flag was used to let us incrementally introduce debug records
into LLVM, however everything is now using records. It serves no
purpose now, so delete it.

Add Metadata::PoisonGeneratingIDs containing IDs of poison-generating
metadata to allow easier re-use.

PR: https://github.com/llvm/llvm-project/pull/123188

This fixes all the places that hit the new assertion added in
https://github.com/llvm/llvm-project/pull/106524 in tests. That is,
cases where the value passed to the APInt constructor is not an N-bit
signed/unsigned integer, where N is the bit width and signedness is
determined by the isSigned flag.

The fixes either set the correct value for isSigned, set the
implicitTrunc flag, or perform more calculations inside APInt.

Note that the assertion is currently still disabled by default, so this
patch is mostly NFC.

Check that all users of a Function are CallBase rather than CallInst
when performing alias analysis using actual arguments in the calling
function, as this check is also valid for Invoke instructions.

This allows replacing the existing check with an assert, as the Function
only being used by CallBase derived instructions is a precondition of
the transform.

This addresses post-commit review on #106216.

Teach Argument Promotion to perform alias analysis on actual arguments
of Calls to a Function, to try to prove that all Calls to the Function
do not modify the memory pointed to by an argument. This surfaces more
opportunities to perform Argument Promotion in cases where simply
looking at a Function's instructions is insufficient to prove that the
pointer argument is not invalidated before all loads from it.

This reverts commit 959448fbd6bc6f74fb3f9655b1387d0e8a272ab8.
Reverting because multiple test failures e.g.
  https://lab.llvm.org/buildbot/#/builders/187/builds/1290
  https://lab.llvm.org/buildbot/#/builders/153/builds/9389
and maybe a few others.