Add FIR resolve test (call extension from extension)

compiler/fir/resolve/testData/resolve/extension.kt

@@ -0,0 +1,5 @@
+fun String.foo() {}
+
+fun String.bar() {
+    foo()
+}

compiler/fir/resolve/testData/resolve/extension.txt

@@ -0,0 +1,6 @@
+FILE: extension.kt
+    public final fun R|kotlin/String|.foo(): R|kotlin/Unit| {
+    }
+    public final fun R|kotlin/String|.bar(): R|kotlin/Unit| {
+        <Unresolved name: foo>#()
+    }