enhance(webhook): add select all and deselect all buttons for custom events (#35980)

Adds `Select All` and `Deselect All` buttons to the custom events
section of the webhook form. This is useful when you need all events but
one.

- The buttons toggle every event checkbox and keep the unsaved-changes
prompt working
- Fix the "Trigger On" radio spacing by removing a leftover Fomantic
checkbox margin

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

templates/webhook/new.tmpl

@@ -9,7 +9,7 @@
 		{{template "repo/settings/webhook/link_menu" ctx.RootData}}
 	</div>
 </h4>
-<div class="ui attached segment">
+<div class="ui attached segment" data-global-init="initCompWebHookEditorForm">
 	{{template "repo/settings/webhook/gitea" ctx.RootData}}
 	{{template "repo/settings/webhook/gogs" ctx.RootData}}
 	{{template "repo/settings/webhook/slack" ctx.RootData}}