KT-28324 More exact startOffset for function/constructor declarations

Function/constructor declaration start offset is the start offset of the
corresponding declaration token, if available.

compiler/testData/ir/sourceRanges/declarations/classProperties.kt

@@ -0,0 +1,78 @@
+package test
+
+class Test {
+
+    val test0 = 42
+
+
+    /**
+     * comment
+     */
+    val test1 = 42
+
+
+    @Suppress(
+        "UNUSED_VARIABLE"
+    )
+    val test2 = 42
+
+
+    private
+    val test3 = 42
+
+
+    val test4 get() = 42
+
+
+    val test5
+        get() = 42
+
+
+    val test6
+        /**
+         * comment
+         */
+        get() = 42
+
+
+    val test7
+        @Suppress(
+            "UNUSED_VARIABLE"
+        )
+        get() = 42
+
+
+    var test8 = 42
+
+
+    var test9 = 42; private set
+
+
+    var test10 = 42
+        private set
+
+
+    var test11 = 42
+        set(value) {
+            field = value
+        }
+
+
+    var test12 = 42
+        /**
+         * comment
+         */
+        set(value) {
+            field = value
+        }
+
+
+    var test13 = 42
+        @Suppress(
+            "UNUSED_VARIABLE"
+        )
+        set(value) {
+            field = value
+        }
+
+}