Rust

Minor: Move `LimitPushdown` tests to be in the same file as the code #36743

Job	Run time
Check cargo fmt	40s
Check License Header	2m 10s
linux build test	2m 1s
build with wasm-pack	2m 0s
cargo test (macos-aarch64)	2m 12s
Verify MSRV (Min Supported Rust Version)	2m 1s
Verify Vendored Code	50s
cargo check datafusion	1s
cargo check functions	1s
cargo doc	1s
cargo check no default features	1s
cargo test datafusion-cli (amd64)	1s
cargo test doc (amd64)	1s
cargo examples (amd64)	1s
Run sqllogictest with Postgres runner	1s
cargo test pyarrow (amd64)	1s
verify benchmark results (amd64)	1s
check Cargo.toml formatting	1s
clippy	1s
check configs.md and ***_functions.md is up-to-date	1s
cargo test (amd64)	1s
	12m 8s

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