Folder option for more DAMs

The "Extra Prefix" option can now be set in the site-level settings for Cloudflare R2, DigitalOcean Spaces, and Google Cloud Storage DAMs. This option restricts all uploads and browsing to a specified folder.

Features:

• "Extra prefix" option is now supported for Cloudflare R2, DigitalOcean Spaces, and Google Cloud Storage DAMs.

Fixes:

• Fixed a bug related to snippets inside rich text inputs.
• Fixed incorrect text shown when installing a new GitHub app.
• Improved error handling and reporting for S3 DAMs.
• Fixed a potential crash related to date fields in the Save modal.
• Fixed a bug where the _enabled_editors configuration option wasn't always respected.