Rust

Remove all allocations in metrics system #21

Job	Run time
Check cargo fmt	38s
cargo check	4m 27s
build with wasm-pack	2m 26s
cargo test (macos)	2m 53s
Verify MSRV (Min Supported Rust Version)	4m 25s
cargo test (macos-aarch64)	3m 30s
Verify Vendored Code	57s
cargo test (win64)	7m 18s
check configs.md is up-to-date	0s
clippy	0s
cargo test hash collisions (amd64)	0s
check Cargo.toml formatting	0s
cargo doc	0s
cargo test (amd64)	0s
cargo test datafusion-cli (amd64)	0s
cargo test doc (amd64)	0s
cargo examples (amd64)	0s
Run sqllogictest with Postgres runner	0s
cargo test pyarrow (amd64)	0s
verify benchmark results (amd64)	0s
	26m 34s

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