[JITLink][AArch32] Implement Armv5 ldr-pc stubs and use them for all pre-v7 targets (#79082)

This stub type loads an absolute address directly into the PC register.
It's the simplest and most compatible way to implement a branch
indirection across the entire address space (and probably the slowest as
well). It's the ideal fallback for all targets for which we did not
(yet) implement a more performant solution.