[BE IR] Skip comments for determining startOffset of declaration

compiler/testData/ir/sourceRanges/comments.kt

@@ -0,0 +1,34 @@
+// One-line comment
+class Foo {
+
+    // Several
+    // lines
+    // of
+    // oneline
+    // commentaries
+    inner class Inner /* comment for constructor */ private constructor(x: Int) {
+        /** dangling comment at the end of body*/
+    } // Comment for closing bracket
+
+    /*
+    very
+    long
+    multiline
+    comment
+     */
+    protected open fun foo(y: Int) { // Comment for opening bracket
+
+    /* Comment for closing bracket */ }
+
+    /**
+     * Javadoc comment
+     */
+    val x: Int = 42
+        // Comment for getter
+        get() = field + 1
+        // Dangling comment
+
+    fun test() {
+        foo(/* comment inside call */ 42)
+    }
+}