Refactor Excel rendering and scan pipeline for improved performance

[cmendible]

Description

Refactor Excel rendering and scan pipeline for improved performance

Issue reference

We strive to have all PR being opened based on an issue, where the problem or feature have been discussed prior to implementation.

Please reference the issue this PR will close: #901

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

• Code compiles correctly
• Created/updated tests
• Unit tests passing

[codecov-commenter]

Codecov Report

❌ Patch coverage is 28.90933% with 541 lines in your changes missing coverage. Please review.
✅ Project coverage is 23.03%. Comparing base (1432167) to head (d0374ad).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/scanners/plugins/sqlesu/sqlesu.go	0.00%	87 Missing ⚠️
internal/graph/graph_scanner.go	0.00%	60 Missing ⚠️
internal/scanners/resources.go	0.00%	52 Missing ⚠️
internal/scanners/plugins/region/availability.go	0.00%	48 Missing ⚠️
internal/scanners/defender.go	0.00%	45 Missing ⚠️
internal/scanners/arc_sql.go	0.00%	37 Missing ⚠️
internal/scanners/azure_policy.go	0.00%	33 Missing ⚠️
internal/scanners/diagnostics_settings.go	0.00%	30 Missing ⚠️
internal/renderers/excel/excel.go	68.53%	15 Missing and 13 partials ⚠️
internal/scanners/plugins/openai/throttling.go	0.00%	24 Missing ⚠️
... and 13 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #902      +/-   ##
==========================================
+ Coverage   21.23%   23.03%   +1.80%     
==========================================
  Files         107      104       -3     
  Lines        7550     7436     -114     
==========================================
+ Hits         1603     1713     +110     
+ Misses       5833     5618     -215     
+ Partials      114      105       -9     

Flag	Coverage Δ
unittests	23.03% <28.90%> (+1.80%)	⬆️

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

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[cmendible]

LGTM