added benchmarks for G_T #111

Job	Run time
set-msrv	4s
linux_foreign (aarch64-unknown-linux-gnu, 1.68.2, aarch64)	47m 2s
bench	2m 28s
windows (x86_64-pc-windows-msvc, stable)	3m 9s
macos (1.63)	2m 43s
clippy_check	1m 26s
macos (stable)	1m 7s
linux (i686-unknown-linux-gnu, 1.63, sudo apt update && sudo apt install gcc-multilib)	25m 19s
Checking fmt and docs	1m 35s
linux (i686-unknown-linux-gnu, stable, sudo apt update && sudo apt install gcc-multilib)	26m 4s
linux (x86_64-unknown-linux-gnu, 1.63)	5m 9s
linux (x86_64-unknown-linux-gnu, stable)	1m 35s
	1h 57m 41s

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