varargs[typed] should behave more like typed

[Graveflo]

This fixes an oversight with a change that I made a while ago.

Basically, these two snippets should both compile. Currently the varargs version will fail.

template s(d: typed)=discard
proc something()=discard
proc something(x:int)=discard

s(something)

template s(d: varargs[typed])=discard
proc something()=discard
proc something(x:int)=discard

s(something)

Potentially unrelated, but this works currently for some reason:

template s(a: varargs[typed])=discard
proc something()=discard
proc something(x:int)=discard

s:
  something

also, this works:

template s(b:untyped, a: varargs[typed])=discard
proc something()=discard
proc something(x:int)=discard

s (g: int):
  something

but this doesn't, and the error message is not what I would expect:

template s(b:untyped, a: varargs[typed])=discard
proc something()=discard
proc something(x:int)=discard

s (g: int), something

So far as I can tell, none of these issues persist for me after the code changes in this PR.

[Graveflo]

I was a bit lost putting this together. With the varargs ast spec and implicitConv. I also think that actingF = f[0] should be actingF = f.base but I don't want to re-run the CI just for that.

[github-actions]

Thanks for your hard work on this PR!
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