support parameter that forces QPU execution

[spreinhardt]

qbsolv's decision about when to use the classical tabu solver and when to use the QPU can be opaque, and the algorithm has changed and probably will change again. Sometimes users want to know that they're using the QPU, to ensure their permissions/token/etc. are all set up properly, or to compare classical/quantum performance. Having a parameter that forces qbsolv to use the QPU will clear up any such confusion.

[levchCode]

Also would be fantastic to get the number of calls to the QPU, so people could estimate the all QPU time used (for D-Wave Leap)