Add post-routing optimisations for `optimisation_level=2`. #247

Job	Run time
IQM - Build and test module (ubuntu-22.04)	1m 29s
IQM - Build and test module (ubuntu-22.04)	2m 6s
IQM - Build and test module (macos-12)	1m 11s
IQM - Build and test module (macos-12)	2m 45s
IQM - Build and test module (windows-2022)	1m 23s
IQM - Build and test module (windows-2022)	3m 23s
Publish to pypi	0s
Publish to pypi	0s
Build docs	0s
Build docs	0s
Publish docs	0s
Publish docs	0s
	12m 17s

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