Libflutter engine rework

[pieter-scholtz]

Adding support profiling mode and ability to look for libflutter_engine.so in the asset bundle.

[ardera]

if you fix the things I commented on it LGTM

[ardera]

few small things then it's done

[ardera]

Just tried running, I get an error when trying to run in profile mode.

In line

flutter-pi/src/flutter-pi.c

Line 2013 in e2d1853

if (flutterpi.flutter.runtime_mode == kRelease) {

, you need to check if runtime_mode == kProfile too, otherwise the app.so is not loaded.