[LoongArch] Support load/store of dso_local PIC global values

lowerGlobalAddress added by D128427 can be used for PIC. The actual condition is
that the global value needs to be dso_local (a dso_preemptable one needs GOT
indirection).

load-store.ll has UB due to out-of-bounds load/store. Fix the UB in the variable
test and add an array test. Note: NOPIC array index is currently wrong.

Reviewed By: wangleiat

Differential Revision: https://reviews.llvm.org/D129977