[doclint] move doclint testing to golden

This patch:
- move doclint testing to golden
- refactor doclint/lint.js to drop specs and everything

utils/doclint/test/01-class-errors/01-class-errors.txt

@@ -0,0 +1,3 @@
+[MarkDown] Non-existing class found: Bar
+[MarkDown] Non-existing class found: Baz
+[MarkDown] Class not found: Other

utils/doclint/test/01-class-errors/doc.md

@@ -0,0 +1,5 @@
+### class: Foo
+
+### class: Bar
+
+### class: Baz

utils/doclint/test/01-class-errors/foo.js

@@ -0,0 +1,2 @@
+class Foo {
+}

utils/doclint/test/01-class-errors/other.js

@@ -0,0 +1,2 @@
+class Other {
+}