Implement CSS-only input toggling, refactor related forms

UX/Translation changes:

- new teams: remove redundant tooltips that don't add meaningful information
  - move general information to table fieldset
- new teams: rename "general" to "custom" access for clarity
- new teams: show labels beside options on mobile

Accessibility:

- semantic form elements allow easier navigation (fieldset, mostly)
- improve better labelling of new teams table
- fix accessibility scan issues
- TODO: the parts that "disable" form elements were not yet touched and
  are not really accessible to screenreaders

Technical:

- replace two JavaScript solutions with one CSS standard
- implement a simpler grid (.simple-grid)
- simplify markup
- remove some webhook settings specific CSS

Testing:

- check more form content for accessibility issues
- but exclude tooltips from the scan :(
- reuse existing form tests from previous PR

web_src/js/features/org-team.js

@@ -1,20 +1,7 @@
 import $ from 'jquery';
-import {hideElem, showElem} from '../utils/dom.js';
 
 const {appSubUrl} = window.config;
 
-export function initOrgTeamSettings() {
-  // Change team access mode
-  $('.organization.new.team input[name=permission]').on('change', () => {
-    const val = $('input[name=permission]:checked', '.organization.new.team').val();
-    if (val === 'admin') {
-      hideElem('.organization.new.team .team-units');
-    } else {
-      showElem('.organization.new.team .team-units');
-    }
-  });
-}
-
 export function initOrgTeamSearchRepoBox() {
   const $searchRepoBox = $('#search-repo-box');
   $searchRepoBox.search({