Reland "[clang] Preserve found-decl when constructing VarTemplateIds" (#82612)

Update include-cleaner tests. Now that we have proper found-decls set up
for VarTemplates, in case of instationtations we point to primary
templates and not specializations. To be changed in a follow-up patch.

GitOrigin-RevId: 5cb2ebc08f6fa42341409b88466c5c266e5839cc
1 file changed