Generate not-null assertions only for descriptors coming from Java

Introduce BindingContext.IS_DECLARED_IN_JAVA, store that info in
JavaDescriptorResolver

compiler/testData/codegen/notNullAssertions/noAssertionsForKotlin.kt

@@ -0,0 +1,13 @@
+class A {
+    val x: Int = 42
+    
+    fun foo(): String = ""
+    
+    class object {
+        val y: Any? = 239
+        
+        fun bar(): String = ""
+    }
+}
+
+fun baz(): String = ""

compiler/testData/codegen/notNullAssertions/noAssertionsForKotlinMain.kt

@@ -0,0 +1,7 @@
+fun bar() {
+    val x = A().x
+    val foo = A().foo()
+    val y = A.y
+    val bar = A.bar()
+    val baz = baz()
+}