Improve error when using dot syntax with an undefined function/method

[jiribenes]

An example from @marvinborner:

val l: List[Int] = [1, 2, 3].delete(4)
//                 ^^^^^^^^^^^^^^^^^^^ error: Cannot typecheck call.

This message originates from:

effekt/effekt/shared/src/main/scala/effekt/Typer.scala

Lines 1263 to 1265 in 73e46d2

	failures match {
	case Nil =>
	Context.abort("Cannot typecheck call.")

If I understood the code correctly, this triggers iff: at the same time don't succeed in finding an overload, but also don't fail [?!]. In my opinion, writing this at thirty to midnight on a Friday, this is the case where we use UFCS to call a method that does not actually exist, hence the attempt at a better error message.

---

TODO Needs some neg tests, ideally also a better fix here (can we say anything about the expected type here?).
I'd also appreciate a double-check: Does this actually happen only in the case I've outlined above (i.e. we cannot find any functions with a passing name, much less a passing type?).

[jiribenes]

According to the Effekt meeting: This needs further investigation, the "0 failures" case probably means something like "we filtered out the failure eagerly, and then therefore didn't give it to this fn".