Add a `BindingKind` for `WithItem` variables #21512

Job	Run time
cargo fmt	21s
benchmarks	13m 16s
cargo clippy	1m 51s
cargo fuzz	8m 2s
cargo test (wasm)	1m 10s
cargo test (linux)	3m 41s
cargo test (windows)	4m 53s
cargo udeps	3m 31s
Determine changes	13s
mkdocs	2m 18s
python package	1m 43s
pre-commit	31s
test scripts	1m 14s
formatter instabilities and black similarity	0s
test ruff-lsp	24s
ecosystem	11m 0s
	54m 8s

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