Improve buffering

[teamclouday]

Some work in progress and plans to improve the app:

• Remove oboe and unnecessary audio buffers
• Use kotlin flow for pub/sub pattern on Android side
• Use protobuf for serialization
• RustApp wave widget render
• Impl protobuf on tcp
• Impl protobuf on udp (no sure if it's possible yet)
• Impl protobuf on adb
• Impl protobuf on bluetooth
• RustApp bluetooth server
• Automatically start recording, tap notification to stop and close service
• Restart audio manager when config has changed
• Better test connection with password (server generate random passcode, client uses passcode to connect)
• RustApp resample input audio stream

Continuing from #38

[teamclouday]

Some note of remaining work for future:

• Auto start audio on Android side
  This will make it much easier to use the app
• Improve TestConnection code to use Protobuf
  Clean up old code
• TestConnection with random passcode
  Not very necessary because it's running in local network
• bluetooth and udp on RustApp
  Not necessary but good to have, can be added some day
• DSP methods like noise suppression/voice activity/echo cancellation
  Good to have, can be added some day
• Resample audio on RustApp
  This is needed when there's a mismatch between Android sample rate and RustApp sample rate. However existing library requires casting samples to f32 first before resampling. It also depends on the supported audio format of the cpal device. This will cause overhead so not implemented for now
  Ideally we only use f32 as output audio format, and cast any type from Android to f32 data stream. I think most audio devices support f32. It makes resampling and other DSP methods easier.