Migrate demo apps to executorch-examples repository

[GregoryComer]

We need to make sure the executorch-examples repo has demo apps ready for 0.6 release.

[metascroy]

@nil-is-all what is the status on this? The ExecuTorch 0.6 release is on Thursday (4/24)?

[nil-is-all]

@nil-is-all what is the status on this? The ExecuTorch 0.6 release is on Thursday (4/24)?

Hi @metascroy, committed the changes here after local tests were successful, except for a CoreML backend failure due to invalid iOS version. @shoumikhin is taking a look.

[metascroy]

Is this done now that the cherry pick is merged @nil-is-all @shoumikhin @mergennachin ?