[OpenMP] Add more identifier to created shared globals

Currenly we push some variables to a global constant containing shared
memory as an optimization. This generated constant had internal linkage
and should not have collided with any known identifiers in the
translation unit. However, there have been observed cases of this
optimiztaion unintentionally colliding with undocumented PTX
identifiers. This patch adds a suffix to the created globals to
hopefully bypass this.

Depends on D118059

Reviewed By: tianshilei1992

Differential Revision: https://reviews.llvm.org/D118068