Make `ChainSelStarvation` carry an `Enclosed` #4942

Job	Run time
Build and test (8.10.7, default, all)	42m 52s
Build and test (9.6.6, default, all)	28m 23s
Build and test (9.10.1, default, all)	27m 14s
Deploy documentation to GitHub Pages	0s
Run benchmarks	0s
	1h 38m 29s

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