native interop: fix syslog on Apple arm64, stop starting getprop

[FreeAndNil]

Fixed

• LocalSyslogAppender passed a variadic argument to syslog(3), audit da18b6f-f046
  • on Apple arm64 a variadic argument goes on the stack, a fixed one in a register, so the callee
    read a slot the runtime never wrote: stack bytes in the system log, or a crash
  • proved by a probe on macOS 26.6.2 arm64, green on Linux and x64
  • variadic is not an option, CoreCLR refuses a __arglist P/Invoke, so only the two fixed
    parameters are declared and the record goes in as the format string with every % doubled
  • logged text, record length and every platform that already worked are unchanged

Changed

• Android detection started a process, audit da18b6f-f048
  • SystemInfo ran getprop ro.build.user at type initialisation on every Unix host, off PATH,
    so the first match there decided the answer
  • now /system/bin/getprop, and the platform itself off net462
• The FormatMessage buffer was released by the wrong allocator, audit da18b6f-f045
  • the API allocates with LocalAlloc, the ref string marshalling freed it as COM task memory
  • now out IntPtr, PtrToStringUni over the returned length, LocalFree in a finally
  • hygiene, not a fix: a probe found the block inside the process heap

Tests

• both probes are gone, each replaced by the regression test of its fix
• the f048 and f046 tests fail against the old code; f045 has none, hence hygiene