[CSSPGO] Minor tweak for inline candidate priority tie breaker

When prioritize call site to consider for inlining in sample loader, use number of samples as a first tier breaker before using name/guid comparison. This would favor smaller functions when hotness is the same (from the same block). We could try to retrieve accurate function size if this turns out to be more important.

Differential Revision: https://reviews.llvm.org/D99370