Allow backup with a pure wireless setup.

[mikedlr]

If there is a pure wireless setup, then it's impossible to connect to the phone and get it's IP address and port configuration until the debugging connection has been set up. Also, every time a new connection is made, the user has to do manual work to read the security code from the phone and give it to the pairing command. In this situation, I think it makes more sense to have the user set up a static connection and to leave that connection in place all the time.

This patch reorganizes the startup so that the wireless vs USB question happens as soon as possible and then disables killing and restarting the adb server if wireless is to be used.

I have not tested this with the old (pre Android 11) wireless setup and I think that the patch breaks that. Android 11 is already EOL, so my feeling is that support for it should be removed with a documentation pointer to the last version of open-android-backup that it would work with. If I get some feedback about this I may update the patch, either to make the old version work as it used to or to or to delete the old code.

[mikedlr]

What I realised after investigating that there's no encryption on ADB backup, so whilst wireless backup is possible, I think it's not justifiable as a public feature. This should maybe be replaced with something equivalent using SSH?

Leaving this PR open for now but I think it should be closed by removing the feature unless there's a simple way to do the backup securely.