Include the descriptor in `keychain::Changeset` #5284

Job	Run time
Check WASM	47s
Build and test (stable, true, --no-default-features)	2m 38s
Check no_std	32s
Build and test (stable, true, --all-features)	2m 42s
Rust fmt	16s
Build and test (1.63.0, --no-default-features)	3m 34s
Build and test (1.63.0, --all-features)	3m 23s
clippy_check	24s
	14m 16s

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