Rewrite VarArg application taking `scala.collection.Seq`

[MasseGuillaume]

seen in https://github.com/scalikejdbc/scalikejdbc/pull/887/files#diff-0b7a8f44eeac5b6ce7571b09b0bffe98L77

in 2.13

val a: scala.collection.Seq[Any] = Seq()
def f(x: Any*): Unit = ()
f(a: _*)

type mismatch;
[error]  found   : Seq[Any] (in scala.collection) 
[error]  required: Seq[Any] (in scala.collection.immutable) 
[error]   f(a: _*)
[error]     ^

compiles in 2.12 and 2.13:

val a: scala.collection.Seq[Any] = Seq()
def f(x: Any*): Unit = ()
f(a.toSeq: _*)

summary:

input:

f(a: _*)

output:

f(a.toSeq: _*)

[julienrf]

For this case I'm not sure we want to apply this solution. Maybe it's better if the user changes its datatype to be an immutable.Seq from the beginning so that the call toSeq is not necessary.

But we could provide such a rewrite, still, and make opt in so that users ca'can decide whether to use it or not.