Allow attempting to install incompatible apps

Detecting whether an app is compatible can be unreliable: for instance, it may be possible to install apps targeting an API level <23 on Android 14+ if the Disable Target API Block LSPosed module is installed, but F-Droid shows them as incompatible.

Suggestion: There should be a button to force attempting to install an incompatible app anyway, if showing incompatible apps is enabled in the settings. This is kind of the opposite of #1570; IMO the ideal approach is a middle ground where the user is warned that the installation will probably fail or the app probably won't work, but there's an option to try it anyway. Also related is #2698, which asks for F-Droid itself to be able to bypass target API limitations (via the privileged extension).

As an example, an old version of Clip Stack, targeting API level 22 is the only open source clipboard manager I've found that's not tied to a specific keyboard, and it works fine on my Android 14, with just minor visual glitches, using the Disable Target API Block and the Clipboard Whitelist LSPosed modules.

Likewise, ideally, contrary to #614 (closed), incompatible updates should be shown as installable if the currently installed version of the app has been installed via F-Droid, and is considered incompatible for the same reason as the update: if I managed to install it anyway, presumably I want the update too if it's incompatible for the same reason the installed version is supposedly incompatible. (I don't know if there is any app that's getting updates, but there's a point in installing which on a phone on which it's listed as incompatible. With new SDK levels adding new restrictions, it's plausible that in a few years the most functional version of certain apps like Termux will be incompatible with the newest Android by default, and will only be installable with trickery, but will nevertheless get updates.)