Add Boolean? == const to elvis conversion and vice versa #KT-15368 Fixed

Convert elvis to equality check implemented as inspection due
code style guide

idea/testData/intentions/nullableBooleanEqualityCheckToElvis/.intention

@@ -0,0 +1 @@
+org.jetbrains.kotlin.idea.intentions.NullableBooleanEqualityCheckToElvisIntention

idea/testData/intentions/nullableBooleanEqualityCheckToElvis/eqFalse.kt

@@ -0,0 +1,6 @@
+fun foo() {
+    val a: Boolean? = null
+    if (a<caret> == false) {
+
+    }
+}

idea/testData/intentions/nullableBooleanEqualityCheckToElvis/eqFalse.kt.after

@@ -0,0 +1,6 @@
+fun foo() {
+    val a: Boolean? = null
+    if (!(a ?: true)) {
+
+    }
+}

idea/testData/intentions/nullableBooleanEqualityCheckToElvis/eqTrue.kt

@@ -0,0 +1,6 @@
+fun foo() {
+    val a: Boolean? = null
+    if (a<caret> == true) {
+
+    }
+}

idea/testData/intentions/nullableBooleanEqualityCheckToElvis/eqTrue.kt.after

@@ -0,0 +1,6 @@
+fun foo() {
+    val a: Boolean? = null
+    if (a ?: false) {
+
+    }
+}

idea/testData/intentions/nullableBooleanEqualityCheckToElvis/flexible.kt

@@ -0,0 +1,4 @@
+fun foo() {
+    val a = java.lang.Boolean.valueOf("true")
+    if (a<caret> == true) {}
+}

idea/testData/intentions/nullableBooleanEqualityCheckToElvis/flexible.kt.after

@@ -0,0 +1,4 @@
+fun foo() {
+    val a = java.lang.Boolean.valueOf("true")
+    if (a ?: false) {}
+}

idea/testData/intentions/nullableBooleanEqualityCheckToElvis/notEqFalse.kt

@@ -0,0 +1,6 @@
+fun foo() {
+    val a: Boolean? = null
+    if (a<caret> != false) {
+
+    }
+}

idea/testData/intentions/nullableBooleanEqualityCheckToElvis/notEqFalse.kt.after

@@ -0,0 +1,6 @@
+fun foo() {
+    val a: Boolean? = null
+    if (a ?: true) {
+
+    }
+}

idea/testData/intentions/nullableBooleanEqualityCheckToElvis/notEqTrue.kt

@@ -0,0 +1,6 @@
+fun foo() {
+    val a: Boolean? = null
+    if (a<caret> != true) {
+
+    }
+}

idea/testData/intentions/nullableBooleanEqualityCheckToElvis/notEqTrue.kt.after

@@ -0,0 +1,6 @@
+fun foo() {
+    val a: Boolean? = null
+    if (!(a ?: false)) {
+
+    }
+}