Update JS dependencies (#15033)

* Update JS dependencies

- Update all JS dependencies
- For octicons, rename trashcan to trash
- For svgo, migrate to v2 api, output seems to have slightly changed but icons look the same
- For stylelint, update config, fix custom property duplicates
- For monaco, drop legacy Edge support
- For eslint, enable new rules, fix new issues
- For less-loader, remove deprecated import syntax

* update svgo usage in generate-images and rebuild logo.svg with it

templates/base/delete_modal_actions.tmpl

@@ -1,6 +1,6 @@
 <div class="actions">
 	<div class="ui red basic inverted cancel button">
-		{{svg "octicon-trashcan"}}
+		{{svg "octicon-trash"}}
 		{{.i18n.Tr "modal.no"}}
 	</div>
 	<div class="ui green basic inverted ok button">

templates/base/head_navbar.tmpl

@@ -100,7 +100,7 @@
 							class="ui button mini compact basic icon fitted poping up"
 							data-content="{{.i18n.Tr "repo.issues.cancel_tracking"}}"
 							data-position="top right" data-variation="small inverted"
-						>{{svg "octicon-trashcan"}}</button>
+						>{{svg "octicon-trash"}}</button>
 					</form>
 				</div>
 			</div>