Migrate deprecations in core, compiler, idea, tests

Replacing deprecated Char.toInt() with Char.code and
Number.toChar() with Number.toInt().toChar(), where Number is not Int.

KT-23451

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/ConstLowering.kt

@@ -60,7 +60,7 @@ class ConstTransformer(private val context: JsIrBackendContext) : IrElementTrans
             }
             return when {
                 expression.kind is IrConstKind.Char ->
-                    lowerConst(charClassSymbol, IrConstImpl.Companion::int, IrConstKind.Char.valueOf(expression).toInt())
+                    lowerConst(charClassSymbol, IrConstImpl.Companion::int, IrConstKind.Char.valueOf(expression).code)
 
                 expression.kind is IrConstKind.Long ->
                     createLong(IrConstKind.Long.valueOf(expression))