Controlled by a new ACE variable.

Fixes #11276

...including: in chat messages and file sending UI.

Also, don't generate wrong URIs like 'file://file:/path' when opening
'file:/path', and properly escape paths: 'file:///¿Qué%3F' <- '/¿Qué?'.

* Don't treat altitude as part of longitude
* Detect more invalid URIs

* Remove URIType.UNKNOWN
* Remove special handling of JID-like strings.  This almost never happens,
  and if it does, it's only due to some unsanitized input, e.g. server contact
  addresses blindly turned into hyperlinks with no validation (to be improved).
* Misc.

Improves debuggability, obviates formatting the errors.

Fixes #11272

Use the newer extension_point() call, which does not replay calls
on plugin activation.

Fixes #11269

Improves the situation for #11263

Fixes #11263

With the switch to pyproject.toml build isolation is used by default.
As flatpak build runs in offline mode, no dependencies could be downloaded
to the isolated environment. That's why build failed.

GUPnPIgd uses libsoup3 which is incompatible with Gajims usage of
libsoup2. This disables loading until Gajim switches to libsoup3.

Fixes #11183

This is only needed once, for notifications.