gh-148868: Increase test coverage for `cmath.isinf` (#148869) #2321

Job	Run time
aarch64-unknown-linux-gnu/gcc	7m 42s
x86_64-unknown-linux-gnu/gcc-free-threading	6m 59s
x86_64-apple-darwin/clang	15m 58s
x86_64-unknown-linux-gnu/gcc	10m 30s
aarch64-apple-darwin/clang	11m 6s
	52m 15s

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