WIP: Mailings: Add a Review Bounces screen

[mlutfy]

Overview

Admins should be warned when there is a high bounce rate, and they should be encouraged to review their bounces so that they can better deal with the situation.

This PR adds a "Review Bounces" menu under Mailings, with a FormBuilder-based screen.

Before

Admins might notice a high bounce rate if they calculate it manually while looking at a specific mailing, but they won't be alerted about it. They might also not know about the Reports > CiviMail > Bounces (which is nice, but messy by default, not sane default filters).

After

(todo: update screenshot: I added the contact name)

TODO

• Form/Search to view recent bounces
• Fix navigation menu item
• See if we can use the same SearchKit/FormBuilder for the "view single email bounces", "view all bounces" and "view a specific mailing bounces". And do the same for unsubscribes and opt-outs.
• System Check for high bounce rate
• SearchKit action to remove "on hold" (because sometimes it bounced for the wrong reason)

Wishlist:

• Form/Search should limit to "last 10 days" or something like that, instead of listing all bounces
• Display the email? I'm not sure if that will kill performance. Makes it easier to spot that the problem is, for example, with Microsoft, or filter by email domain.

[civibot]

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