Rust

Remove all allocations in metrics system #19

Job	Run time
cargo check	3m 55s
build with wasm-pack	2m 23s
cargo test (macos)	3m 36s
cargo test (macos-aarch64)	3m 39s
Verify Vendored Code	48s
cargo test (win64)	8m 32s
Check cargo fmt	36s
Verify MSRV (Min Supported Rust Version)	6m 42s
check configs.md is up-to-date	0s
cargo test hash collisions (amd64)	0s
check Cargo.toml formatting	0s
clippy	0s
cargo doc	0s
cargo test (amd64)	0s
cargo test datafusion-cli (amd64)	0s
cargo test doc (amd64)	0s
cargo examples (amd64)	0s
cargo test pyarrow (amd64)	0s
Run sqllogictest with Postgres runner	0s
verify benchmark results (amd64)	0s
	30m 11s

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