configure hardening: _FORTIFY_SOURCE=3 support

Please add _FORTIFY_SOURCE=3 support to the configure script.

Compared to _FORTIFY_SOURCE=2, _FORTIFY_SOURCE=3 should cover more cases and improve security hardening: https://developers.redhat.com/articles/2022/09/17/gccs-new-fortification-level https://developers.redhat.com/articles/2023/02/06/how-improve-application-security-using-fortifysource3

Currently it uses _FORTIFY_SOURCE=2 only. https://gitlab.torproject.org/tpo/core/tor/-/blob/aeb2e24a75bd5cbe7fab9f49cda01ac111c55433/configure.ac#L1327

Debian 12 Bookworm's glibc and GCC version should bring support for _FORTIFY_SOURCE=3

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