[red-knot] Support `assert_type` #38564

Job	Run time
cargo build (release)	0s
cargo fmt	15s
Determine changes	10s
mkdocs	2m 36s
pre-commit	3m 12s
python package	1m 22s
benchmarks	5m 6s
cargo fuzz build	5m 25s
cargo build (msrv)	4m 15s
cargo clippy	1m 56s
cargo shear	25s
cargo test (linux)	1m 50s
cargo test (linux, release)	3m 44s
cargo test (wasm)	1m 41s
cargo test (windows)	6m 4s
test scripts	1m 7s
formatter instabilities and black similarity	0s
ecosystem	2m 42s
fuzz parser	0s
test ruff-lsp	40s
	42m 30s

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