[FIR] Add checker for uninitialized properties

compiler/testData/diagnostics/tests/lateinit/local/uninitialized.fir.kt

@@ -0,0 +1,24 @@
+// !LANGUAGE: +LateinitLocalVariables
+
+fun test1() {
+    lateinit var s: String
+    <!UNINITIALIZED_VARIABLE!>s<!>.length
+}
+
+fun test2() {
+    lateinit var s: String
+    run {
+        s = ""
+    }
+    s.length
+}
+
+fun almostAlwaysTrue(): Boolean = true
+
+fun test3() {
+    lateinit var s: String
+    if (almostAlwaysTrue()) {
+        s = ""
+    }
+    <!UNINITIALIZED_VARIABLE!>s<!>.length
+}

compiler/testData/diagnostics/tests/lateinit/local/uninitialized.kt

@@ -1,4 +1,3 @@
-// FIR_IDENTICAL
 // !LANGUAGE: +LateinitLocalVariables
 
 fun test1() {