Add `ProofSizeExt` to benchmarks #5156

Job	Run time
check-dependency-rules	10s
set-image	9s
check-workspace	22s
check-markdown	14s
fmt	1m 1s
check-rust-feature-propagation	1m 53s
check-umbrella	2m 5s
check-toml-format	57s
test-rust-features	1m 54s
	8m 45s

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