Refacto: move rules context into a structured object

[Guts]

This PR is a following up of #481.

It's mainly a code structure improvement which aims to improve readability, testing and maintainability:

• create an object
• move it from utils to profiles since it's only related to QDT profiles management
• add methods to export as dict and JSON
• add unit test
• use it in documentation and GenericJob.filter_on_rules

Next (spoiler alert): a CLI command to generate the rules context to make the rules writing more handy

[sonarcloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.47%. Comparing base (1b76259) to head (241d859).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #491      +/-   ##
==========================================
+ Coverage   70.19%   70.47%   +0.27%     
==========================================
  Files          48       48              
  Lines        3013     3028      +15     
  Branches      648      653       +5     
==========================================
+ Hits         2115     2134      +19     
+ Misses        710      704       -6     
- Partials      188      190       +2     

Flag	Coverage Δ
unittests	69.84% <100.00%> (+0.28%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
qgis_deployment_toolbelt/jobs/generic_job.py	89.15% <100.00%> (ø)
qgis_deployment_toolbelt/jobs/job_splash_screen.py	67.85% <ø> (ø)
qgis_deployment_toolbelt/profiles/rules_context.py	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes

[jmkerloch]

LGTM !