Add netmask to get ip

[hulto]

What type of PR is this?

/kind cleanup
/kind feature

What this PR does / why we need it:

Add netmask CIDR to sys.get_ip
Remove get_ip dependency on pnet crate.

Which issue(s) this PR fixes:

Unblocks #484

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 72.02%. Comparing base (80eea9c) to head (2e3476b).

Files	Patch %	Lines
implants/lib/eldritch/src/sys/get_ip_impl.rs	80.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #659      +/-   ##
==========================================
- Coverage   72.08%   72.02%   -0.06%     
==========================================
  Files         175      175              
  Lines       12018    12008      -10     
==========================================
- Hits         8663     8649      -14     
- Misses       3141     3145       +4     
  Partials      214      214              

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[Cictrone]

just one small typo, otherwise lgtm!