[ASTMatcher] Correct memoization bug ignoring direction (descendants or ancestors)

Summary:
In ASTMatcher, when we have `has(...)` and `hasParent(...)` called with the same internal matcher on the same node, the memoization process will mix-up the two calls because the direction of the traversal is not part of the memoization key.

This patch adds this information.

Reviewers: klimek

Reviewed By: klimek

Subscribers: Godin, njames93, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D80025