Consider restoring custom vf2_post_layout

[bachase]

As part of #256, all custom transpiler passes were removed as benchmarking showed the customizations were not providing additional gate savings or compilation time improvements compared with the native Qiskit passes. However, the benchmarks were not testing compilation with any coupling constraints. We should add such benchmarks, and retest the customized vf2_post_layout to see if it should be restored.

[Misty-W]

Althoug not currently part of the automated pipeline, there is code for benchmarking different layouts in
https://github.com/unitaryfund/ucc/blob/main/benchmarks/scripts/generate_layouts.py .

Here's the results from a local run I did before merging the custom VF2 passes: #169 (comment)