Add sampling support

[antalszava]

Context
The PennyLane-Orquestra plugin allows computing expectation values. Obtaining samples of circuit runs is not available at the moment.

Orquestra provides a step for running a circuit and obtaining measurement outcomes. This step could be used on the server-side of the plugin for adding sampling support.

Note on exact devices

It is worth noting, that for exact devices, sampling would include computing the probability distribution of measurement outcomes. This would require additional logic to allow for arbitrary Hermitian operators when obtainig bitstrings in the computational basis.