Revert "Revert "Reapply D70800: Fix AArch64 AAPCS frame record chain""

This reverts commit bc9a29b9.

The reasoning that this patch was wrong was itself incorrect
(see discussion on llvm-commits). This patch does seem to be exposing
a latent SVE code generation bug on non-public tests, which should
not block a correctness fix for public, non-SVE use cases.