feat: parallel audit requests

[fabriziosestito]

Description

This PR implements parallel audit requests to the policy server.
The parallelism is currently set to 100 requests, but in the future, we could expose this value to the user through the CLI so that it can be tuned.

Gnu time output

Before the fix on a cluster with ~300 resources and 15 policies:

Percent of CPU this job got: 79%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:41.24

After the fix

Percent of CPU this job got: 109%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:30.42

In the case of slower policies (for instance policies using context-aware capabilities) is safe to assume that the elapsed time difference should be higher.

[codecov]

Codecov Report

Attention: Patch coverage is 85.71429% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 72.80%. Comparing base (7e56394) to head (8d19288).
Report is 2 commits behind head on main.

Files	Patch %	Lines
internal/scanner/scanner.go	85.71%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #220      +/-   ##
==========================================
+ Coverage   72.37%   72.80%   +0.43%     
==========================================
  Files           6        6              
  Lines         637      662      +25     
==========================================
+ Hits          461      482      +21     
- Misses        115      117       +2     
- Partials       61       63       +2     

Flag	Coverage Δ
unit-tests	72.80% <85.71%> (+0.43%)	⬆️

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[flavio]

Nice!

[flavio]

This is going to be part of the final 1.11 release

CC @brunorene

[flavio]

This fixes #217

[viccuad]

LGTM!

[viccuad]

This feels more a feature than a fix, for it appear as such in the GH release it is enough to change the PR title.