Fix(sigmatch): allow varargs[T] to accept overloaded symbol

There was a bug that params wouldn't be matched if the param was
overloaded and the candidate type was varargs. This checks the base type
of the `varargs` and then will to an overloaded symbol if in a macros or
template.

Fixes nim-lang#19446
Fixes nim-lang#13913

compiler/sigmatch.nim

@@ -2233,8 +2233,13 @@ proc paramTypesMatch*(m: var TCandidate, f, a: PType,
         # XXX this is still all wrong: (T, T) should be 2 generic matches
         # and  (int, int) 2 exact matches, etc. Essentially you cannot call
         # typeRel here and expect things to work!
-        let r = typeRel(z, f, arg[i].typ)
+        var r = typeRel(z, f, arg[i].typ)
         incMatches(z, r, 2)
+        if r == isNone:
+          if userConvMatch(c, m, f, a, arg) == nil and f.kind == tyVarargs:
+            if f.n == nil:
+              if typeRel(m, base(f), a) == isGeneric:
+                r = typeRel(m, base(f), a)
         if r != isNone:
           z.state = csMatch
           case x.state
@@ -2258,6 +2263,9 @@ proc paramTypesMatch*(m: var TCandidate, f, a: PType,
       # See tsymchoice_for_expr as an example. 'f.kind == tyUntyped' should match
       # anyway:
       if f.kind in {tyUntyped, tyTyped}: result = arg
+      elif m.calleeSym != nil and m.calleeSym.kind in {skMacro, skTemplate} and
+           f.kind == tyVarargs:
+        result = arg
       else: result = nil
     else:
       # only one valid interpretation found: