Re-land parsing and printing for Clang function types.

This reverts commit e805fe486e, which reverted
the change earlier. The problem was caused due to a simultaneous change to some
code by the PR with parsing and printing for Clang function types (#28737)
and the PR which introduced Located<T> (#28643).

This commit also includes a small change to make sure the intersecting region
is fixed: the change is limited to using the fields of Located<T> in the
`tryParseClangType` lambda.

lib/Frontend/CompilerInvocation.cpp

@@ -227,6 +227,8 @@ static void ParseModuleInterfaceArgs(ModuleInterfaceOptions &Opts,
 
   Opts.PreserveTypesAsWritten |=
     Args.hasArg(OPT_module_interface_preserve_types_as_written);
+  Opts.PrintFullConvention |=
+    Args.hasArg(OPT_experimental_print_full_convention);
 }
 
 /// Save a copy of any flags marked as ModuleInterfaceOption, if running