refactor(firewall): move duplicated rule parsing code into own functions

[phm07]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 64.64646% with 35 lines in your changes missing coverage. Please review.

Project coverage is 59.69%. Comparing base (474b945) to head (5475367).
Report is 1 commits behind head on main.

Files	Patch %	Lines
internal/cmd/firewall/add_rule.go	61.22%	16 Missing and 3 partials ⚠️
internal/cmd/firewall/create.go	73.17%	5 Missing and 6 partials ⚠️
internal/cmd/firewall/delete_rule.go	25.00%	1 Missing and 2 partials ⚠️
internal/cmd/firewall/replace_rules.go	60.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #796      +/-   ##
==========================================
- Coverage   59.73%   59.69%   -0.04%     
==========================================
  Files         210      210              
  Lines        7641     7598      -43     
==========================================
- Hits         4564     4536      -28     
+ Misses       2435     2424      -11     
+ Partials      642      638       -4     

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