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/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/FirAnnotationArgumentVisitor.kt

@@ -35,7 +35,7 @@ internal object FirAnnotationArgumentVisitor : AnnotationArgumentVisitor<Unit, F
 
     override fun visitCharValue(value: CharValue, data: FirAnnotationArgumentVisitorData) {
         data.builder.type = ProtoBuf.Annotation.Argument.Value.Type.CHAR
-        data.builder.intValue = value.value.toLong()
+        data.builder.intValue = value.value.code.toLong()
     }
 
     override fun visitDoubleValue(value: DoubleValue, data: FirAnnotationArgumentVisitorData) {

compiler/fir/fir-serialization/src/org/jetbrains/kotlin/fir/serialization/constant/ConstantValue.kt

@@ -53,7 +53,7 @@ internal class ByteValue(value: Byte) : IntegerValueConstant<Byte>(value) {
 internal class CharValue(value: Char) : IntegerValueConstant<Char>(value) {
     override fun <R, D> accept(visitor: AnnotationArgumentVisitor<R, D>, data: D): R = visitor.visitCharValue(this, data)
 
-    override fun toString(): String = "\\u%04X ('%s')".format(value.toInt(), getPrintablePart(value))
+    override fun toString(): String = "\\u%04X ('%s')".format(value.code, getPrintablePart(value))
 
     private fun getPrintablePart(c: Char): String = when (c) {
         '\b' -> "\\b"