Squash PTs into Lyrebrid

APK size is a problem on Android. We have a package size budget of about 100 megabytes to be allowed to be hosted on the Google Play store. In addition, mobile network conditions can kind of suck, so downloading large APKs is bad UX all-around.

We recently hit the size limit in the Tor Browser 13.5 series, and had to do a bit of trimming and build optimisations to get back within our budget.

@shelikhoo recently squashed the web-tunnel PT into lyrebird, which gave us some more breathing room. We should follow suit with the remaining PTs to de-duplicate the common functionality between them.

@JeremyRand experimented with and presented busy box compression which basically automates this squashing, and got substantial size improvements. We decided in that session to avoid the busy-box tool in favor of something more supported (eg manually squashing the projects) to minimize build toolchain headaches for the apps team (in exchange for more headaches for the anti-censorshp team; sorry!)