Fix: ignore diagnostic input and escape collector fields

[Rom1-B]

Checklist before requesting a review

Please delete options that are not relevant.

• I have performed a self-review of my code.
• I have added tests (when available) that prove my fix is effective or that my feature works.
• I have updated the CHANGELOG with a short functional description of the fix or new feature.
• This change requires a documentation update.

Description

• It fixes #N/A
• The connection diagnostic on an authorization now always targets the provider's own IMAP host, port and security setting instead of whatever values were submitted with the form.
• The application's "Mail collectors" tab now escapes each collector's host and login before displaying them, consistent with the escaping already used elsewhere in this table.

Screenshots (if appropriate):