Update signing workflow

[martincostello]

• Update AuthenticodeLint to a version targeting .NET 8.
• Set environment variables for Azure Key Vault to use with future versions of the sign tool.

Tested in #2322.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.39%. Comparing base (0969c55) to head (23e17ac).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2323   +/-   ##
=======================================
  Coverage   85.39%   85.39%           
=======================================
  Files         313      313           
  Lines        7461     7461           
  Branches     1126     1126           
=======================================
  Hits         6371     6371           
  Misses        745      745           
  Partials      345      345           

Flag	Coverage Δ
linux	85.39% <ø> (+0.02%)	⬆️
macos	85.36% <ø> (-0.03%)	⬇️
windows	85.36% <ø> (ø)

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

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