Reland "[AMDGPU] Add AMDGPU-specific module splitting (#89245)"

(with fix for ubsan)

This enables the --lto-partitions option to work more consistently.

This module splitting logic is fully aware of AMDGPU modules and their
specificities and takes advantage of
them to split modules in a way that avoids compilation issue (such as
resource usage being incorrectly represented).

This also includes a logging system that's more elaborate than just
LLVM_DEBUG which allows
printing logs to uniquely named files, and optionally with all value
names hidden so they can be safely shared without leaking informatiton
about the source. Logs can also be enabled through an environment
variable, which avoids the sometimes complicated process of passing a
-mllvm option all the way from clang driver to the offload linker that
handles full LTO codegen.