Add `BasePass.get_pre_conditions` and `BasePass.get_post_conditions` #6277

Job	Run time
Check tket library version	16s
Build and test pytket (ubuntu)	8m 43s
Build and test pytket (macos) (macos-13)	10m 56s
Build and test pytket (windows)	13m 21s
Build and test pytket (macos) (macos-15)	5m 8s
Build and test (tket)	0s
Build and test (tket)	0s
Check documentation build	0s
Check C++ code formatting	0s
Publish pytket coverage	0s
Check pytket line and branch coverage	4s
All build and test jobs successful (or skipped)	1s
	38m 29s

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