DEV: Cleanup & modernize

[Arkshine]

This PR fixes minor issues, modernizes, and does some cleanup.

• Uses FormKit in the modal ¹
  • Increases random ID length from 8 to 10 characters to avoid getting a popup saying ID is unsafe.
  • Groups the iframe-related checkboxes with a title for consistency, and simplifies the locale.
• decorateCooked -> decorateCookedElement
• Removes version from withPluginApi (TC is already pinned to 3.5.0.beta1-dev)
• Renders the launch button with a glimmer component
  • The preview renders now the button (click is disabled). Before, there was nothing.
  • Fixes the username not filled when Jitsi loads. It replaces jitsiAPI.executeCommand by specifying the userInfo object.
  • Adds { once: true } param to jitsiAPI.addEventListener
  • Chat: fixed direct link when spaces are used by encoding room ID.
• Updates lint configs
• Adds system tests

Locales:

• Added: modal.iframe_title
• Modified: modal.desktop_iframe, modal.mobile_iframe

Footnotes

1. Before/After
   
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