Android: Support for managing proxies and certificate authorities

[baltpeter]

This PR brings support for fully automating traffic collection on Android. For that, it adds the following functions on the platform API object:

• installCertificateAuthority() and removeCertificateAuthority() to install or remove a certificate authority as a trusted system CA on the device. (https://github.com/tweaselORG/meta/issues/18#issuecomment-1437057934)
• setProxy() to either set/disable the global proxy settings or enabled/disable a WireGuard tunnel depending on whether the newly introduced wireguard capability is used. WireGuard is automatically installed and configured on the device if enabled. (#25, https://github.com/tweaselORG/meta/issues/19, #38)

In addition, it adds the following unrelated functions that were necessary to implement the above:

• setAppBackgroundBatteryUsage() to configure an app's battery optimization settings, and thus whether it is allowed to run in the background. (#34)
• stopApp() to, you guessed it, (force-)stop an app. (#36)
• isAppInstalled() to check whether an app is already installed on the device. (#40)

None of these features are implemented for iOS yet. That will be my next step, some reverse-engineering has already happened for that.

[baltpeter]

Now with fully automated WireGuard setup in ensureDevice()! \o/

I have so far only tested this on a physical Android 13 device.

[baltpeter]

@zner0L I've made the changes you requested (can't re-request review because you didn't submit a new one).