Downgrade autoconf

Troy Curtis, Jr requested to merge downgrade-autoconf into main

@timsoft noted that the autoconf caused issues building on distros with an older autoconf. While autoconf doesn't always need to be run by the users of the software, it turns out 2.69 works well with the current macros so there is no reason not to downgrade the version a bit.

I'm also adding centos stream9 to the build tests to help catch similar issues in the future.

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