Move `Adapt` to a weak dependency #657

Job	Run time
test (1.0, ubuntu-latest, x64)	4m 14s
test (1.0, windows-latest, x64)	7m 14s
test (1.0, macOS-latest, x64)	4m 49s
test (1.6, ubuntu-latest, x64)	3m 55s
test (1.6, windows-latest, x64)	7m 59s
test (1.6, macOS-latest, x64)	4m 30s
test (1, ubuntu-latest, x64)	3m 38s
test (1, windows-latest, x64)	4m 30s
test (1, macOS-latest, x64)	4m 12s
test (~1.10.0-0, ubuntu-latest, x64)	3m 43s
test (~1.10.0-0, windows-latest, x64)	4m 35s
test (~1.10.0-0, macOS-latest, x64)	6m 21s
test (nightly, ubuntu-latest, x64)	4m 48s
test (nightly, windows-latest, x64)	5m 40s
test (nightly, macOS-latest, x64)	8m 28s
test (ubuntu-latest, 1, x86)	4m 39s
	1h 23m 15s

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