refactor: move app code into packages #417

Job	Run time
Build integration artifacts	3m 51s
Rust lint and unit tests	3m 16s
Packages and VS Code extension	36s
Client lint, build, and tests	42s
Android emulator integration	6m 32s
CLI simulator integration	8m 35s
JS API simulator integration	3m 50s
	27m 22s

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