[FE] Prohibit property initializers with context receivers

compiler/testData/diagnostics/tests/extensions/contextReceivers/noBackingField.fir.kt

@@ -0,0 +1,15 @@
+interface A {
+    fun a(): Int
+}
+interface B {
+    fun b(): Int
+}
+
+context(A)
+val a = 1
+
+context(A, B)
+var b = 2
+
+context(A, B)
+val c get() = <!UNRESOLVED_REFERENCE!>a<!>() + <!UNRESOLVED_REFERENCE!>b<!>()

compiler/testData/diagnostics/tests/extensions/contextReceivers/noBackingField.kt

@@ -0,0 +1,15 @@
+interface A {
+    fun a(): Int
+}
+interface B {
+    fun b(): Int
+}
+
+context(A)
+val a = <!CONTEXT_RECEIVERS_WITH_BACKING_FIELD!>1<!>
+
+context(A, B)
+var b = <!CONTEXT_RECEIVERS_WITH_BACKING_FIELD!>2<!>
+
+context(A, B)
+val c get() = a() + b()

compiler/testData/diagnostics/tests/extensions/contextReceivers/noBackingField.txt

@@ -0,0 +1,19 @@
+package
+
+public val a: kotlin.Int = 1
+public var b: kotlin.Int
+public val c: kotlin.Int
+
+public interface A {
+    public abstract fun a(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface B {
+    public abstract fun b(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}