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

js/js.parser/src/org/jetbrains/kotlin/js/parser/sourcemaps/JSON.kt

@@ -13,7 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-
+@file:Suppress("DEPRECATION") // TODO: needs an intensive rework for new Char API
 package org.jetbrains.kotlin.js.parser.sourcemaps
 
 import java.io.*

js/js.parser/src/org/jetbrains/kotlin/js/parser/sourcemaps/SourceMapParser.kt

@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+@file:Suppress("DEPRECATION") // TODO: needs an intensive rework for new Char API
 package org.jetbrains.kotlin.js.parser.sourcemaps
 
 import java.io.File