Add char binary operations to JVM codegen tests.

compiler/testData/codegen/box/binaryOp/callNullable.kt

@@ -5,6 +5,8 @@ fun box(): String {
     val a4: Long? = 1.plus(1)
     val a5: Double? = 1.0.plus(1)
     val a6: Float? = 1f.plus(1)
+    val a7: Char? = 'A'.plus(1)
+    val a8: Int? = 'B'.minus('A')
 
     if (a1!! != 2.toByte()) return "fail 1"
     if (a2!! != 2.toShort()) return "fail 2"
@@ -12,6 +14,8 @@ fun box(): String {
     if (a4!! != 2L) return "fail 4"
     if (a5!! != 2.0) return "fail 5"
     if (a6!! != 2f) return "fail 6"
+    if (a7!! != 'B') return "fail 7"
+    if (a8!! != 1) return "fail 8"
 
     return "OK"
 }