[modules] Correctly parse LateParsedTemplates in case of dependent modules.

[modules] Correctly parse LateParsedTemplates in case of dependent modules.

While parsing LateParsedTemplates, Clang assumes that the Global DeclID matches
with the Local DeclID of a Decl. This is not the case when we have multiple
dependent modules , each having their own LateParsedTemplate section. In such a
case, a Local/Global DeclID confusion occurs which leads to improper casting of
FunctionDecl's.

This commit creates a Vector to map the LateParsedTemplate section of each
Module with their module file and therefore resolving the Global/Local DeclID
confusion.

Reviewed By: rsmith

Differential Revision: https://reviews.llvm.org/D86514