[API] Add "before" query to ListIssueComments and ListRepoIssue… (#9685)

* add "before" query to ListIssueComments and ListRepoIssueComments

* Add TEST

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: Antoine GIRARD <sapk@users.noreply.github.com>

models/fixtures/comment.yml

@@ -13,6 +13,7 @@
   issue_id: 1 # in repo_id 1
   content: "good work!"
   created_unix: 946684811
+  updated_unix: 946684811
 -
   id: 3
   type: 0 # comment
@@ -20,6 +21,7 @@
   issue_id: 1 # in repo_id 1
   content: "meh..."
   created_unix: 946684812
+  updated_unix: 946684812
 -
   id: 4
   type: 21 # code comment
@@ -63,4 +65,4 @@
   review_id: 10
   tree_path: "README.md"
   created_unix: 946684812
-  invalidated: true
+  invalidated: true