workspace: fix pointer scanning, add duplicate prefix error

[BrettMayson]

Checks /include/, /optionals/, /addons/ for prefix files instead of /

Adds a new error if there are any duplicate prefix files

[codecov]

Codecov Report

Attention: Patch coverage is 68.75000% with 10 lines in your changes missing coverage. Please review.

Project coverage is 69.2%. Comparing base (8216250) to head (6078b78).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
libs/workspace/src/lib.rs	68.7%	10 Missing ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
libs/common/src/prefix.rs	96.9% <ø> (ø)
libs/workspace/src/lib.rs	89.1% <68.7%> (-5.3%)	⬇️