Test match behaviour of both Configuration and ConfigurationSequence

[akaIDIOT]

No functional changes, just testing this works (and keeps working) as intended.

[github-actions]

Comparing median (lower is better) metric of benchmarks between this PR's target (63b97c5) and the HEAD of this PR (d2229d1):

	3.10	3.11	3.12	3.13	3.14	PyPy 3.10	PyPy 3.11
test_benchmark_get	-2%	+3%	-3%	+4%	+1%	+1%	-0%
test_benchmark_get_dotted	+2%	-0%	-1%	+3%	-0%	+5%	+1%
test_benchmark_getattr	+0%	+1%	+0%	+2%	-1%	-6%	-2%
test_benchmark_getitem	-0%	+3%	-2%	+3%	+1%	+2%	-1%
test_benchmark_getitem_dotted	+4%	+1%	-0%	+1%	-0%	+3%	-1%
test_benchmark_init_full_overlap	-1%	+0%	-1%	+9%	-0%	-1%	-2%
test_benchmark_init_no_overlap	-1%	-1%	+0%	+6%	+0%	-3%	-0%
test_benchmark_init_partial_overlap	-1%	+1%	+0%	+9%	+0%	-1%	-1%
test_benchmark_reference_chain	-0%	-1%	+1%	+3%	-1%	+3%	+3%
test_benchmark_splat_args	+1%	+0%	+1%	+4%	+1%	-0%	-6%
test_benchmark_spread_kwargs	+0%	+3%	-3%	+5%	+0%	+4%	-1%

(This comment will be updated on subsequent pushes)