Tests

Pass around Arc<Package> rather than cloning them #1750

Job	Run time
quick-test	4m 23s
test (macOS-latest, stable)	4m 53s
test (macOS-latest, nightly)	9m 43s
tests-from-tarball (ubuntu-latest)	2m 15s
test (macOS-latest, 1.78)	5m 29s
test (ubuntu-latest, stable)	4m 38s
cargo-mutants (0, cargo)	6m 38s
test (ubuntu-latest, nightly)	7m 47s
pr-mutants	0s
cargo-mutants (1, cargo)	8m 51s
test (ubuntu-latest, 1.78)	4m 22s
cargo-mutants (2, cargo)	8m 22s
cargo-mutants (3, cargo)	9m 47s
test (windows-latest, stable)	7m 34s
cargo-mutants (4, cargo)	8m 38s
test (windows-latest, nightly)	15m 15s
test (windows-latest, 1.78)	7m 20s
cargo-mutants (5, cargo)	10m 29s
cargo-mutants (6, cargo)	8m 57s
cargo-mutants (7, cargo)	13m 14s
cargo-mutants (8, cargo)	9m 28s
cargo-mutants (9, cargo)	7m 8s
overall-result	1s
	2h 45m 12s

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