Partition and ExtendableSquareMatrix data structures #450

Job	Run time
run-tests (ubuntu-latest)	2m 22s
run-test-performance-base (ubuntu-latest)	2m 33s
warnings-new (ubuntu-latest)	2m 6s
run-tests (macos-latest)	3m 57s
run-test-performance-base (macos-latest)	2m 50s
warnings-new (macos-latest)	1m 47s
run-test-performance (ubuntu-latest)	2m 28s
run-test-performance (macos-latest)	4m 43s
warnings-base (ubuntu-latest)	2m 0s
warnings-base (macos-latest)	1m 47s
compare-versions (ubuntu-latest)	4s
compare-versions (macos-latest)	4s
code-coverage	1m 43s
compare-performance (ubuntu-latest)	17s
compare-performance (macos-latest)	24s
	29m 5s

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