fix semcase on tySequence and tyObject #20283 #19682 (#20339)

* fix semcase on tySequence and tyObject #20283 #19682

* use better arg name

* avoiding returns nil use errorNode instead, clean code

* use efNoDiagnostics flag

* remove tests/errmsgs/t19682.nim

* combine 2 test cases to one file

compiler/semcall.nim

@@ -402,6 +402,9 @@ proc resolveOverloads(c: PContext, n, orig: PNode,
     if overloadsState == csEmpty and result.state == csEmpty:
       if efNoUndeclared notin flags: # for tests/pragmas/tcustom_pragma.nim
         template impl() =
+          result.state = csNoMatch
+          if efNoDiagnostics in flags:
+            return
           # xxx adapt/use errorUndeclaredIdentifierHint(c, n, f.ident)
           localError(c.config, n.info, getMsgDiagnostic(c, flags, n, f))
         if n[0].kind == nkIdent and n[0].ident.s == ".=" and n[2].kind == nkIdent: