[Spec tests] Add tests for character-literals

compiler/tests-spec/testData/codegen/box/linked/expressions/constant-literals/character-literals/p-4/pos/2.1.kt

@@ -0,0 +1,23 @@
+// WITH_RUNTIME
+
+/*
+ * KOTLIN CODEGEN BOX SPEC TEST (POSITIVE)
+ *
+ * SPEC VERSION: 0.1-218
+ * PLACE: expressions, constant-literals, character-literals -> paragraph 4 -> sentence 2
+ * NUMBER: 1
+ * DESCRIPTION: character literal codepoint is equal to the unicode symbol codes
+ */
+
+fun box(): String {
+    val a = '\u0000'
+    val c = ' ' //u+0020
+    val cMax = '￿' //u+ffff
+    val aMax = '\uffff'
+    if (a.toShort() == 0x0000.toShort()
+        && c.toShort() == 0x0020.toShort()
+        && cMax.toShort() == 0xffff.toShort()
+        && aMax.toShort() == 0xffff.toShort())
+        return "OK"
+    return "NOK"
+}

compiler/tests-spec/testData/codegen/box/linked/expressions/constant-literals/character-literals/testsMap.json

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+{
+  "4": {
+    "pos": {
+      "2": [
+        {
+          "specVersion": "0.1-218",
+          "casesNumber": 0,
+          "description": "character literal codepoint is equal to the unicode symbol codes",
+          "unexpectedBehaviour": false
+        }
+      ]
+    }
+  }
+}