[DPE-4062] Improve displayed error message if charm was deployed without `--trust` flag

[lucasgameiroborges]

Issue

K8s charms that create resources in a RBAC enabled environment need to be deployed with the --trust flag, otherwise they don't work. If a user deploys PGB k8s charm without that flag, there is no clear message indicating the issue.

Solution

• Adds a integration test to see if charm enters blocked status if not deployed with --trust.
• Adds a check in K8s resource creation functions to catch for 403 forbidden errors. ==> This check was added everywhere lightkube.Client().get is used. Maybe overkill, but better safe than sorry, I think?
• Adds unit tests

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 80.00000% with 6 lines in your changes missing coverage. Please review.

Project coverage is 70.63%. Comparing base (c36b92b) to head (e01dd08).

Files	Patch %	Lines
src/charm.py	80.00%	1 Missing and 5 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #319 +/- ## ========================================== + Coverage 70.35% 70.63% +0.28% ========================================== Files 8 8 Lines 1167 1192 +25 Branches 213 218 +5 ========================================== + Hits 821 842 +21 + Misses 269 268 -1 - Partials 77 82 +5 ```

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