Format spaces around in keyword

Fixes: KT-10680

idea/formatter/src/org/jetbrains/kotlin/idea/formatter/kotlinSpacingRules.kt

@@ -167,6 +167,7 @@ fun createSpacingBuilder(settings: CodeStyleSettings, builderUtil: KotlinSpacing
 
             around(AS_KEYWORD).spaces(1)
             around(IS_KEYWORD).spaces(1)
+            around(IN_KEYWORD).spaces(1)
             aroundInside(IDENTIFIER, BINARY_EXPRESSION).spaces(1)
 
             // before LPAR in constructor(): this() {}

idea/testData/formatter/In.after.kt

@@ -0,0 +1,5 @@
+fun f() {
+    if (1 in intArrayOf()) {
+
+    }
+}

idea/testData/formatter/In.kt

@@ -0,0 +1,5 @@
+fun f() {
+    if (1   in   intArrayOf()) {
+
+    }
+}

idea/tests/org/jetbrains/kotlin/formatter/FormatterTestGenerated.java

@@ -349,6 +349,12 @@ public class FormatterTestGenerated extends AbstractFormatterTest {
             doTest(fileName);
         }
 
+        @TestMetadata("In.after.kt")
+        public void testIn() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/formatter/In.after.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("InfixCall.after.kt")
         public void testInfixCall() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("idea/testData/formatter/InfixCall.after.kt");