[AsmPrinter] Reject ptrtoint to larger size in lowerConstant()

When using a ptrtoint to a size larger than the pointer width in a
global initializer, we currently create a ptr & low_bit_mask style
MCExpr, which will later result in a relocation error during object
file emission.

This patch rejects the constant expression already during
lowerConstant(), which results in a much clearer error message
that references the constant expression at fault.

This fixes https://github.com/llvm/llvm-project/issues/56400,
for certain definitions of "fix".

Differential Revision: https://reviews.llvm.org/D130366