FIR JS: add K2 variants of all other JS tests

except tests that are not possible to add without some modifications in
the test infra. See todos on the commented-out test declarations

compiler/testData/codegen/box/when/exhaustiveBoolean.kt

@@ -1,5 +1,5 @@
 // LANGUAGE: -ProhibitSimplificationOfNonTrivialConstBooleanExpressions
-// IGNORE_BACKEND_K2: JVM_IR
+// IGNORE_BACKEND_K2: JVM_IR, JS_IR
 // FIR status: don't support legacy feature
 fun box() : String = when (true) {
     ((true)) -> "OK"