[red-knot] Add diagnostic for invalid unpacking #37832

Job	Run time
mkdocs	12s
cargo fmt	22s
cargo build (release)	0s
Determine changes	11s
pre-commit	17s
python package	12s
benchmarks	1s
cargo build (msrv)	1s
cargo clippy	1s
cargo fuzz build	1s
cargo shear	1s
cargo test (linux)	1s
cargo test (linux, release)	1s
cargo test (windows)	1s
formatter instabilities and black similarity	1s
cargo test (wasm)	1s
test scripts	1s
fuzz parser	1s
ecosystem	1s
test ruff-lsp	1s
	1m 28s

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