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

core/descriptors/src/org/jetbrains/kotlin/resolve/constants/constantValues.kt

@@ -85,7 +85,7 @@ class CharValue(value: Char) : IntegerValueConstant<Char>(value) {
 
     override fun <R, D> accept(visitor: AnnotationArgumentVisitor<R, D>, data: D) = visitor.visitCharValue(this, data)
 
-    override fun toString() = "\\u%04X ('%s')".format(value.toInt(), getPrintablePart(value))
+    override fun toString() = "\\u%04X ('%s')".format(value.code, getPrintablePart(value))
 
     private fun getPrintablePart(c: Char): String = when (c) {
         '\b' -> "\\b"