quantity checking functions

[andrewgsavage]

• Closes Quantity checking functions for downstream libraries #1813
• Executed pre-commit run --all-files with no errors
• The change is fully covered by automated unit tests
• Documented in docs/ as appropriate
• Added an entry to the CHANGES file

[codspeed-hq]

CodSpeed Performance Report

Merging #1867 will improve performances by 21.71%

_{Comparing andrewgsavage:is_quantity_ (ef91a23) with master (f9e139e)}

Summary

⚡ 1 improvements
✅ 438 untouched benchmarks

Benchmarks breakdown

	Benchmark	master	andrewgsavage:is_quantity_	Change
⚡	test_op1[neg-int_kilometer]	160.4 µs	131.8 µs	+21.71%