fix: serialize user-defined window functions to proto #34980

Job	Run time
cargo check	7m 47s
Check cargo fmt	47s
build with wasm-pack	2m 44s
Check License Header	2m 20s
cargo test (macos)	15m 19s
cargo test (macos-aarch64)	14m 30s
Verify MSRV (Min Supported Rust Version)	9m 0s
Verify Vendored Code	50s
cargo test (win64)	1h 16m 42s
cargo test datafusion-cli (amd64)	4m 21s
cargo test (amd64)	11m 54s
cargo doc	4m 42s
clippy	6m 7s
cargo test doc (amd64)	16m 29s
cargo examples (amd64)	14m 10s
Run sqllogictest with Postgres runner	3m 49s
cargo test pyarrow (amd64)	3m 6s
verify benchmark results (amd64)	13m 0s
check Cargo.toml formatting	3m 1s
check configs.md and ***_functions.md is up-to-date	3m 25s
cargo test hash collisions (amd64)	17m 40s
	3h 51m 43s

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