Add missing includes for FreeBSD 14 in pal_networkstatistics.c

[Thefrank]

This patch is already in ports version of dotnet for FreeBSD.

This PR upstreams the patch with a FreeBSD ifdef

  In file included from /runtime/src/native/libs/System.Native/pal_networkstatistics.c:61:
  /crossrootfs/x64/usr/include/netinet/tcp_var.h:310:17: error: field has incomplete type 'struct callout'
          struct callout t_callout;
                         ^
  /crossrootfs/x64/usr/include/netinet/tcp_var.h:310:9: note: forward declaration of 'struct callout'
          struct callout t_callout;
                 ^
  /crossrootfs/x64/usr/include/netinet/tcp_var.h:471:13: error: field has incomplete type 'struct osd'
          struct osd      t_osd;          /* storage for Khelp module data */
                          ^
  /crossrootfs/x64/usr/include/netinet/tcp_var.h:471:9: note: forward declaration of 'struct osd'
          struct osd      t_osd;          /* storage for Khelp module data */
                 ^

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[wfurt]

LGTM

[wfurt]

all test failures are know problems.