[flang] Don't complain about implicitly-typed dummy arguments inherited into an IMPLICIT NONE submodule

[klausler]

Summary

When a module procedure's interface is defined in an ancestor (sub)module
with an implicitly typed dummy argument, don't emit a bogus error in
the separate module procedure later if its submodule has IMPLICIT NONE.

Fixes llvm-test-suite/Fortran/gfortran/regression/submodule_26.f90.

[PeteSteinfeld]

All builds and tests correctly and looks good.

flang/lib/Semantics/resolve-names-utils.cpp

void MapSubprogramToNewSymbols(const Symbol &oldSymbol, Symbol &newSymbol,
   }
   mappings->symbolMap[&oldSymbol] = &newSymbol;
   const auto &oldDetails{oldSymbol.get<SubprogramDetails>()};
   auto &newDetails{newSymbol.get<SubprogramDetails>()};
   for (const Symbol *dummyArg : oldDetails.dummyArgs()) {
     if (!dummyArg) {
       newDetails.add_alternateReturn();
     } else if (Symbol *copy{newScope.CopySymbol(*dummyArg)}) {
+      copy->set(Symbol::Flag::Implicit, false);
       newDetails.add_dummyArg(*copy);
       mappings->symbolMap[dummyArg] = copy;
     }
   }
   if (oldDetails.isFunction()) {
     newScope.erase(newSymbol.name());
     if (Symbol *copy{newScope.CopySymbol(oldDetails.result())}) {
       newDetails.set_result(*copy);

flang/test/Semantics/modproc02.f90

+!RUN: %flang_fc1 -fdebug-dump-symbols %s | FileCheck %s
+module m
+  interface
+    module subroutine s(x) ! implicitly typed
+    end
+  end interface
+end
+
+submodule (m) sm
+  implicit none
+ contains
+  !Ensure no error here due to IMPLICIT NONE
+  module procedure s
+  end
+end
+
+!CHECK:  Module scope: m size=0 alignment=1 sourceRange=63 bytes
+!CHECK:    s, MODULE, PUBLIC (Subroutine): Subprogram isInterface (REAL(4) x)
+!CHECK:    sm: Module (m)
+!CHECK:    Subprogram scope: s size=4 alignment=4 sourceRange=26 bytes
+!CHECK:      s (Subroutine): HostAssoc
+!CHECK:      x (Implicit) size=4 offset=0: ObjectEntity dummy type: REAL(4)
+!CHECK:    Module scope: sm size=0 alignment=1 sourceRange=65 bytes
+!CHECK:      s, MODULE, PUBLIC (Subroutine): Subprogram (REAL(4) x) moduleInterface: s, MODULE, PUBLIC (Subroutine): Subprogram isInterface (REAL(4) x)
+!CHECK:      Subprogram scope: s size=4 alignment=4 sourceRange=22 bytes
+!CHECK:        s: HostAssoc
+!CHECK:        x size=4 offset=0: ObjectEntity dummy type: REAL(4)