Generalize FindTypes with CompilerContext to support fuzzy lookup
This patch generalizes the FindTypes with CompilerContext interface to
support looking up a type of unknown kind by name, as well as looking
up a type inside an unspecified submodule. These features are
motivated by the Swift branch, but are fully tested via unit tests and
lldb-test on llvm.org. Specifically, this patch adds an AnyModule and
an AnyType CompilerContext kind.
Differential Revision: https://reviews.llvm.org/D66507