test

Add the 'btree' benchmark. (#381) #2539

Job	Run time
ubuntu-24.04-arm - 3.12	7m 37s
ubuntu-latest - 3.13	8m 25s
macos-latest - 3.14	7m 8s
ubuntu-24.04-arm - 3.10	6m 38s
ubuntu-latest - 3.15-dev free-threading	11m 15s
ubuntu-24.04-arm - 3.11	7m 51s
ubuntu-24.04-arm - 3.14	7m 25s
ubuntu-latest - pypy-3.11	10m 49s
windows-latest - 3.14	12m 10s
ubuntu-latest - 3.14 free-threading	8m 48s
ubuntu-latest - 3.10	7m 38s
ubuntu-24.04-arm - 3.13	7m 45s
ubuntu-latest - 3.11	7m 6s
ubuntu-latest - 3.14	8m 8s
ubuntu-latest - 3.15-dev	10m 16s
ubuntu-24.04-arm - 3.14 free-threading	7m 55s
ubuntu-latest - 3.12	8m 10s
	2h 25m 4s

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