SI-8417 Check adapts of each param section

[som-snytt]

Previously, adaptations like auto-tupling were checked
only on the last param section of an application.

This commit runs the sanity check always.

JIRA: https://issues.scala-lang.org/browse/SI-8417

[adriaanm]

This goes in the right direction in making the check more explicit. Can we push it a bit more and avoid future reorderings of the conditions?

// May warn or error if a Unit or tuple was inserted.
def validate(t: Tree): Tree = {
  val invalidAdaptation = t.symbol != null && !checkValidAdaptation(t, args) // regardless of typer's mode
  if (invalidAdaptation && mode.typingExprNotFun) EmptyTree // only bail if we're typing an expression (and not inside another application)
  else t
}