Expose gateset choice at hugr-to-qir conversion

[trvto]

This can work similarly to the target parameter, will (eventually) invoke lowering to that gateset.

At the moment we support only one gateset but there are technically 3 Gatesets available for H2.

Will need to implement guppy extensions for these gatesets in order to add them.
Also need lowerings from guppy std extension to these gatesets in tket
At some point will also have Sol, etc gatesets