[CSSPGO][PriorityInliner] Do not use block weight to drive callsite inlining.

The priority-based inliner currenlty uses block count combined with callee entry count to drive callsite inlining. This doesn't work well with LTO where postlink inlining is driven by prelink-annotated block count which could be based on the merge of all context profiles. I'm fixing it by using callee profile entry count only which should be context-sensitive.

I'm seeing 0.2% perf improvment for one of our internal large benchmarks with probe-based non-CS profile.

Reviewed By: wenlei

Differential Revision: https://reviews.llvm.org/D120784