[deployment/chef] Fix custom variables handling on Windows

[crobert-1]

Description:

This fixes how Chef handles custom variables for the splunk-otel-collector on Windows deployments. The MSI doesn't support custom variables, it supports a set of known variables. To properly set custom variables we need to use the registry.

Also, update version of the collector being used in testing.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 44.90%. Comparing base (e26dffc) to head (71238d1).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6271      +/-   ##
==========================================
- Coverage   44.90%   44.90%   -0.01%     
==========================================
  Files         390      390              
  Lines       26994    26994              
==========================================
- Hits        12123    12121       -2     
- Misses      14003    14008       +5     
+ Partials      868      865       -3     

☔ View full report in Codecov by Sentry.
📢 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.

[jvoravong]

The changes LGTM. Left a comment for recommendations for how to create related releases, if this PR is updated to change the release strategy that is acceptable.

[pjanotti]

LGTM - the failure is well known and being tracked separately