Switch to codecov (#404) #8

Job	Run time
black	10s
coverage	2m 51s
black_fix	0s
notebooks	20m 6s
minimal	1m 10s
pip_check	47s
unittest_abinit	1m 7s
unittest_gpaw	12m 6s
unittest_mace	2m 14s
unittest_matgl	2m 31s
unittest_old	2m 42s
unittest_matrix (macos-latest, 3.12)	3m 19s
unittest_qe	8m 31s
unittest_matrix (ubuntu-latest, 3.12)	2m 9s
unittest_siesta	1m 46s
unittest_matrix (windows-latest, 3.12)	3m 13s
unittest_matrix (ubuntu-latest, 3.11)	2m 28s
unittest_matrix (ubuntu-latest, 3.10)	2m 20s
autobot	0s
	1h 9m 30s

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