Introduce BoundedValue as a generalization of (low..high) range

Provide BoundedValue-based implementation of InExpressionGenerator,
test it on range of comparable values.
Drop unneeded test (range of comparables is already tested by
ranges/contains/inComparableRanges.kt).

compiler/testData/codegen/box/ranges/contains/inRangeOfComparable.kt

@@ -1,7 +0,0 @@
-// WITH_RUNTIME
-
-fun box(): String {
-    if ("z" in "Alpha" .. "Omega") return "Fail 1"
-    if ("Gamma" !in "Alpha" .. "Omega") return "Fail 2"
-    return "OK"
-}