[Inliner] Preserve llvm.mem.parallel_loop_access metadata

When inlining a call site with llvm.mem.parallel_loop_access metadata, this
metadata needs to be propagated to all cloned memory-accessing instructions.
Otherwise, inlining parts of the loop body will invalidate the annotation.

With this functionality, we now vectorize the following as expected:

  void Body(int *res, int *c, int *d, int *p, int i) {
    res[i] = (p[i] == 0) ? res[i] : res[i] + d[i];
  }

  void Test(int *res, int *c, int *d, int *p, int n) {
    int i;

  #pragma clang loop vectorize(assume_safety)
    for (i = 0; i < 1600; i++) {
      Body(res, c, d, p, i);
    }
  }

llvm-svn: 267949