test

Add bm_base64 covering common base64 module APIs #2386

Job	Run time
ubuntu-latest - 3.13	8m 12s
ubuntu-24.04-arm - 3.10	6m 33s
ubuntu-latest - 3.14 free-threading	9m 32s
ubuntu-24.04-arm - 3.12	7m 34s
ubuntu-latest - 3.14	8m 46s
ubuntu-24.04-arm - 3.11	7m 20s
ubuntu-24.04-arm - 3.13	7m 13s
ubuntu-latest - 3.12	8m 42s
ubuntu-24.04-arm - 3.14	7m 39s
ubuntu-latest - 3.10	7m 21s
ubuntu-latest - pypy-3.11	13m 43s
macos-latest - 3.14	6m 48s
windows-latest - 3.14	14m 4s
ubuntu-latest - 3.15-dev	7m 32s
ubuntu-24.04-arm - 3.14 free-threading	7m 25s
ubuntu-latest - 3.15-dev free-threading	8m 32s
ubuntu-latest - 3.11	8m 30s
	2h 25m 26s

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