Use Depot 8-core runner for ecosystem tests #35967

Job	Run time
cargo fmt	19s
Determine changes	9s
mkdocs	2m 47s
pre-commit	36s
python package	1m 16s
cargo build (msrv)	3m 52s
cargo build (release)	5m 0s
benchmarks	4m 56s
cargo clippy	1m 54s
cargo fuzz	5m 15s
cargo shear	26s
cargo test (linux)	4m 12s
cargo test (wasm)	1m 30s
cargo test (windows)	9m 12s
formatter instabilities and black similarity	4m 10s
test scripts	1m 8s
Fuzz the parser	6m 46s
ecosystem	3m 51s
test ruff-lsp	34s
	57m 53s

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