android: add shortcuts

[mahyarmirrashed]

Fixes tailscale/tailscale#16415

screen-20250716-221150.mp4

[mahyarmirrashed]

@kari-ts Could I get your review on these changes? Thanks :)

[tobiasmcnulty]

Is it possible to hide or disable the shortcuts if "Force enabled connection toggle" ("Prevents the user from disconnecting Tailscale." is enabled via the MDM managed configuration? (Full disclosure: I'm not a Tailscale developer.)

[mahyarmirrashed]

@tobiasmcnulty Yes, I think so. However, you'd need to change it from static shortcuts (the way it is currently) to dynamic shortcuts. I haven't looked into it but it seems like it's just one library to do it: https://developer.android.com/develop/ui/views/launch/shortcuts/creating-shortcuts#dynamic
I can make it as a follow-up PR to this PR. I'd just like to get these changes merged first before putting more time to the second one.

[mahyarmirrashed]

@barnstar Could I get your review on this please?