[red-knot] Ensure a gradual type can always be assigned to itself #39342

Job	Run time
cargo fmt	18s
Determine changes	9s
cargo build (release)	0s
mkdocs	2m 31s
pre-commit	3m 20s
python package	1m 21s
cargo clippy	1m 49s
cargo test (linux, release)	4m 3s
cargo test (windows)	4m 55s
cargo test (linux)	1m 48s
cargo build (msrv)	4m 10s
cargo fuzz build	5m 18s
cargo shear	23s
benchmarks	5m 12s
cargo test (wasm)	1m 41s
test scripts	1m 6s
formatter instabilities and black similarity	0s
ecosystem	2m 41s
test ruff-lsp	42s
fuzz parser	0s
	41m 27s

Provide feedback