Add tls_certificate commands to gsad

[timopollmeier]

This adds the commands create_tls_certificate, delete_tls_certificate,
get_tls_certificate, get_tls_certificates and save_tls_certificate
to gsad.

Checklist:

• Tests N/A
• CHANGELOG Entry

[codecov]

Codecov Report

Merging #1455 into master will decrease coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1455      +/-   ##
==========================================
- Coverage   36.73%   36.72%   -0.01%     
==========================================
  Files         991      991              
  Lines       22191    22191              
  Branches     6088     6089       +1     
==========================================
- Hits         8151     8150       -1     
- Misses      12715    12716       +1     
  Partials     1325     1325

Impacted Files	Coverage Δ
.../src/web/pages/scanconfigs/editnvtdetailsdialog.js	3.22% <0%> (-0.11%)	⬇️
gsa/src/gmp/models/nvt.js	98.75% <0%> (-0.02%)	⬇️

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[bjoernricks]

Looks good. I am not really satisfied with the certificate_bin param name but because certificate has a different validation type it's fine.