Upgrade Rust toolchain to 1.84.0 #38622

Job	Run time
cargo build (release)	0s
cargo fmt	19s
mkdocs	2m 46s
Determine changes	12s
python package	1m 22s
pre-commit	3m 12s
benchmarks	7m 10s
cargo build (msrv)	6m 15s
cargo clippy	4m 3s
cargo fuzz build	6m 29s
cargo shear	25s
cargo test (wasm)	1m 33s
cargo test (linux, release)	3m 36s
cargo test (linux)	1m 42s
cargo test (windows)	5m 58s
formatter instabilities and black similarity	3m 13s
test scripts	59s
fuzz parser	5m 35s
ecosystem	3m 56s
test ruff-lsp	37s
	59m 22s

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