Proposal

Right now, the custom devices feature as is proposed in #78113 defaults all configured custom devices to TargetPlatform.linux_arm64 (maybe linux_<anything> when #78151 is resolved).
That has the following unwanted side effects:

1. for example the VS Code plugin recognizes those devices as linux desktop devices and
2. doesn't show those devices to the user if the linux-desktop feature is disabled
3. prompts the user to activate the linux-desktop feature
4. which is completely unnecessary to work with those devices and may confuse users.

Also, because we reuse the linux target platform(s), all the ApplicationPackages passed for example to CustomDevice.startApp, CustomDevice.installApp, CustomDevice.uninstallApp etc are LinuxApps as well.

It'd maybe be better to use something like TargetPlatform.custom_arm, TargetPlatform.custom_arm64 etc, so we can also implement our own ApplicationPackage for custom devices. Though that may require extra support in any IDE plugins.