Switch default routing/layout method to sabre for opt level 3

[mtreinish]

Summary

This commit switches the default routing and layout method for
optimization level 3 to use SabreSwap and SabreLayout passes. The
quality of results is typically better with sabre than the default
stochastic swap and dense layout we're using now. For optimization
level 3 where we try to produce the best quality result and runtime
is of secondary concern using sabre makes the most sense (especially
after #7036 which improves the runtime performance). Also for
optimization level 3 currently sabre is typically faster because we
increase the number of trials for stochastic swap (which is generally
significantly faster) which slows it down as it's doing more work.
This should improve the quality and speed of the results in general
when running with optimization level 3. In the future we can do more
work to improve the runtime performance of the sabre passes and
hopefully make it fast enough to use for all the optimization levels
which have more constraints on the run time performance than level 3.

Details and comments

Related to #7112 and #7200

[mtreinish]

Marking as on hold until #7036 merges because I don't think we want to do this without having that performance improvement

[mtreinish]

To see the improvement in the quality of results you can look at the nightly benchmarks here:

• https://qiskit.github.io/qiskit/#transpiler_qualitative.TranspilerQualitativeBench.track_depth_transpile_mod8_10_178?p-optimization%20level=3&x-axis=routing%20method&p-layout%20method='dense'&p-layout%20method='sabre'&ram=64GB
• https://qiskit.github.io/qiskit/#transpiler_qualitative.TranspilerQualitativeBench.track_depth_transpile_4mod5_v0_19?ram=64GB&p-optimization%20level=3&p-routing%20method='sabre'&p-layout%20method='dense'&p-layout%20method='sabre'&x-axis=routing%20method
• https://qiskit.github.io/qiskit/#transpiler_qualitative.TranspilerQualitativeBench.track_depth_transpile_4gt10_v1_81?x-axis=routing%20method&python=3.8&p-optimization%20level=3&p-layout%20method='dense'&p-layout%20method='sabre'

Which is comparing the depth of the output circuits at optimization level 3 with different routing and layout method combinations.

[mtreinish]

Also: https://nonhermitian.org/posts/2021/2021-10-31-best_swap_mapper_qiskit.html is relevant here too

[jakelishman]

This is just a straightforwards swap - doesn't look like anything should go wrong, since we're already testing Sabre significantly. I'll look at #7036 as well.

[coveralls]

Pull Request Test Coverage Report for Build 1483085405

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.007%) to 82.557%

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Files with Coverage Reduction	New Missed Lines	%
qiskit/transpiler/preset_passmanagers/level3.py	2	91.98%

Totals
Change from base Build 1483075115:	0.007%
Covered Lines:	49879
Relevant Lines:	60418

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💛 - Coveralls