cargo-apk: Automate adb reverse port forwarding through Cargo.toml metadata

[Jasper-Bekkers]

Fixes #231

This adds a feature so we can set up reverse port forwarding from our Cargo.toml file before the app starts

[package.metadata.android.reverse_port_fwd]
"tcp:1338" = "tcp:1338"
"tcp:1339" = "tcp:1339"

[msiglreith]

Would be nice to have the example from the readme added in our manifest example

[Jasper-Bekkers]

Updated the readme in 4638053

[MarijnS95]

This isn't strictly for http, I'd write Android device connects to `localhost` on port `1338` ....

For demonstration purposes, can we use a different source and destination purposes? e.g. it will be routed to the host on port `XYZ whatever you choose` instead.

[MarijnS95]

I still don't feel entirely confident about having this in adb, we're just building out more and more passthrough commands for adb that don't have much in common with apk building anymore, but I don't have any other alternative 😭 (i.e. a server on the host that makes itself visible to connected adb devices instead, but adb wait-for-device isn't powerful enough). A scriptable pre-apk-start might solve many such things but isn't platform-agnostic either :(

[Jasper-Bekkers]

I still don't feel entirely confident about having this in adb, we're just building out more and more passthrough commands for adb that don't have much in common with apk building anymore

For us, in practice, it means a significantly smoother and less error prone workflow for launching apk's, regardless of how much it has to do with building an apk or not, for us it's fundamental to running one which is why I'm proposing adding this to this tool.

[MarijnS95]

Sure, and as said above we don't really have any clean/proper alternative. At the same time we're one of the very few actively contributing to cargo-apk so I think we can bend it towards our use-cases somewhat.

I'll apply the nits above and merge this, not sure when I'll push out a new (patch) release though (cargo install --git exists, fortunately).