Test

Add `Product` expression and normalising rules #1287

Job	Run time
Test (stable, 2.5.1, ubuntu-latest)	3m 4s
Examples (stable, ubuntu-latest)	2m 3s
Test (stable, 2.5.1, macos-latest)	2m 46s
Examples (stable, macos-latest)	1m 30s
Test (nightly, 2.5.1, ubuntu-latest)	2m 39s
Examples (nightly, ubuntu-latest)	1m 54s
Test (nightly, 2.5.1, macos-latest)	3m 8s
Examples (nightly, macos-latest)	1m 42s
Audit (stable)	2m 10s
Audit (nightly)	2m 47s
	23m 43s

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