[JS IR BE]: support dynamic_var["foo"] = "bar"

Used EQ origin to detect. Added a test to check dynamic_var = "bar" case
is not affected

js/js.translator/testData/box/expression/for/overCollectionWithIndex.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JS_IR
 // EXPECTED_REACHABLE_NODES: 1652
 // CHECK_NOT_CALLED_IN_SCOPE: function=component1 scope=test1
 // CHECK_NOT_CALLED_IN_SCOPE: function=component1 scope=test2

js/js.translator/testData/box/expression/when/whenWithMapRangeClause.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND: JS_IR
 // EXPECTED_REACHABLE_NODES: 1211
 
 package foo