feat: add syslog macros LOG_MASK/LOG_UPTO

[SteveLauC]

Description

Adds syslog C macros to all UNIX targets

1. LOG_MASK
2. LOG_UPTO

They are re-implemented as Rust functions, and tests are added to ensure our Rust implementations have the same behavior as the C macro.

Sources

Link to the musl impl: https://github.com/bminor/musl/blob/61399d4bd02ae1ec03068445aa7ffe9174466bfd/include/syslog.h#L23-L24

Checklist

• Relevant tests in libc-test/semver have been updated
• No placeholder or unstable values like *LAST or *MAX are
  included (see #3131)
• Tested locally (cd libc-test && cargo test --target mytarget);
  especially relevant for platforms that may not be checked in CI

[rustbot]

r? @tgross35

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[SteveLauC]

CI failure seems unrelated, it is due to a failed network call

[SteveLauC]

Ok, now, the CI errors are really related to my patch, the wasi CIs failed because there is no sys/syslog.h header file, I am no WebAssembly expert, should I just simply disable the cc part and tests under these targets?