Convert gr-comment-thread to typescript

The change converts the following files to typescript:

* elements/shared/gr-comment-thread/gr-comment-thread.ts

Change-Id: I25744317ce26edcbf996ee852c5557758408bf94

polygerrit-ui/app/elements/change/gr-change-view/gr-change-view_test.js

diff --git a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view_test.js b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view_test.js
index 4db670f..141df65 100644
--- a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view_test.js
+++ b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view_test.js
@@ -800,6 +800,8 @@
             getAllThreadsForChange: () => THREADS,
             computeDraftCount: () => 0,
           }));
+      element._change = generateChange();
+      element._changeNum = element._change._number;
     });
 
     test('draft threads should be a new copy with correct states', done => {
@@ -920,8 +922,10 @@
 
   suite('Findings comment tab', () => {
     setup(done => {
+      element._changeNum = '42';
       element._change = {
         change_id: 'Iad9dc96274af6946f3632be53b106ef80f7ba6ca',
+        project: 'testRepo',
         revisions: {
           rev2: {_number: 2, commit: {parents: []}},
           rev1: {_number: 1, commit: {parents: []}},