[ADD] runbot_merge: merge dates of PRs in PR dashboard table

Requested by @Williambraecky to make checking over the entire batch
easier when checking if an upgrade exception can be removed.

Also add the info to the batch generalogy table, because why not.

runbot_merge/views/batch.xml

@@ -75,6 +75,7 @@
                                     <field name="name"/>
                                     <field name="target"/>
                                     <field name="all_prs" widget="many2many_tags"/>
+                                    <field name="merge_date"/>
                                 </tree>
                             </field>
                         </group>

runbot_merge/views/templates.xml

@@ -530,6 +530,7 @@ for branch in [*branches, branches.browse(())]:
                 'checked': done or p.status == 'success',
                 'reviewed': done or bool(p.reviewed_by),
                 'attached': done or p.parent_id or not p.source_id,
+                'merge_date': p.merge_date or '',
             })
         state = None
         for i, s in zip(range(2, -1, -1), ['danger', 'success', 'warning']):
@@ -607,9 +608,10 @@ action = batches
                             that's not always the case
                             -->
                             <span t-foreach="ps['prs']" t-as="p"
-                                  t-att-title="p['label']"
+                                  t-att-title="p['label'] + (p['merge_date'] and (f' at ' + str(p['merge_date'])))"
                                   t-att-class="'closed' if p['closed'] else None">
                                 <a t-attf-href="/{{repo.name}}/pull/{{p['number']}}">#<t t-out="p['number']"/></a>
+                                <sup t-if="p['merge_date'] and request.session.debug" t-out="p['merge_date']"/>
                                 <a t-attf-class="fa fa-brands fa-github"
                                    title="Open on Github"
                                    t-att-href="p['github_url']"