refactor: wiki edit form (#38918)

1. the fragile `document.querySelector('.repository.wiki.new
.ui.form')!` is broken (again), rewrite to "data-global-init"
    * regression from #37571 because a new form was added
3. use "form-fetch-action" and JSON response instead of
"RenderWithErrDeprecated"

web_src/js/index.ts

@@ -38,7 +38,7 @@ import {initInstall} from './features/install.ts';
 import {initCompWebHookEditor} from './features/comp/WebHookEditor.ts';
 import {initRepoBranchButton} from './features/repo-branch.ts';
 import {initCommonOrganization} from './features/common-organization.ts';
-import {initRepoWikiForm} from './features/repo-wiki.ts';
+import {initRepoWiki} from './features/repo-wiki.ts';
 import {initRepository, initBranchSelectorTabs} from './features/repo-legacy.ts';
 import {initCaptcha} from './features/captcha.ts';
 import {initRepositoryActions} from './features/repo-actions.ts';
@@ -135,7 +135,7 @@ const initPerformanceTracer = callInitFunctions([
   initRepoReleaseNew,
   initRepoTopicBar,
   initRepoViewFileTree,
-  initRepoWikiForm,
+  initRepoWiki,
   initRepository,
   initRepositoryActions,
   initRepositorySearch,