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Minor tweaks in the grammar
JS backend: for with label, fix KT-5257 JS: for with continue with label fails on runtime, and KT-5262 JS: wrong code for `for` over range when start greater end

 #KT-5257 Fixed
 #KT-5262 Fixed
JS backend: add NotNull annotations
JS backend: add LoopTranslator.kt, move ExpressionVisitor.createWhile and ForTranslator into LoopTranslart, remove foreach package
JS backend: refactor LoopTranslator, add function translateForExpression
JS backend: do not generate extra tmp vars