Improve performance of `buildableOfCollCond`

[mdedetrich]

Current implementation of buildableOfCollCond isn't as performant as it could be, an alternative version such as

@SuppressWarnings(
  Array(
    "scalafix:DisableSyntax.while",
    "scalafix:DisableSyntax.return"
  )
)
@scala.annotation.nowarn("msg=return statement uses an exception")
private def buildableOfCollCond[C <: Iterable[T], T](cond: C => Boolean, g: Gen[C])(implicit
    evb: Buildable[T, C]
): Gen[C] =
  Gen.infiniteLazyList(g).map { ll =>
    val it   = ll.iterator
    val bldr = evb.builder
    while (true) {
      val result = bldr.result()
      if (cond(result)) {
        return result
      }
      bldr ++= it.next()
    }
    return bldr.result()
  }

Note that this version of buildableOfCollCond doesn't actually it (it seems to have termination issues).