RustPackageHelper.py: Update __set_members to avoid duplicates

[Antaeus Kleinert-Strand (antklein)]

Description

• Updates RustPackageHelper to deduplicate Cargo workspace members by path before constructing RustPackage objects.
• Adds unit tests for the __set_members function.
• Also replaces the direct type(...) != str comparison with isinstance() when identifying path-based workspace dependencies.

Some local crates are declared both as Cargo workspace members and as path-based workspace dependencies. The previous implementation placed RustPackage instances in a set, but RustPackage does not define value-based equality or hashing. Separate instances representing the same path were therefore retained as distinct entries.

Collecting Path objects in the set provides value-based deduplication and ensures each workspace package is tested once.

• Impacts functionality?
• Impacts security?
• Breaking change?
• Includes tests?
• Includes documentation?

How This Was Tested

Ran the Rust host-based unit test runner through stuart_ci_build.
Verified that each crate appears only once in the generated Cargo coverage command.
All unit tests are passing.

Integration Instructions

N/A

[mu-automation]

✅ QEMU Validation Passed

Source Dependencies

Repository	Commit
mu_basecore	8fcbf07
mu_tiano_platforms	d966ff0

Results

Platform	Target	Build	Boot	Overall Boot Time	Build Logs	Boot Logs
Q35	DEBUG	✅ success	✅ success	0m 20s	Build Logs	Boot Logs
ArmVirt	DEBUG	✅ success	✅ success	0m 13s	Build Logs	Boot Logs

Workflow run: https://github.com/microsoft/mu_basecore/actions/runs/35126023232

This comment was automatically generated by the Mu QEMU PR Validation workflow.

[Codecov Comments Bot (codecov-commenter)]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (release/202511@9a00f76). Learn more about missing BASE report.

Additional details and impacted files

@@                Coverage Diff                @@
##             release/202511    #1915   +/-   ##
=================================================
  Coverage                  ?    2.23%           
=================================================
  Files                     ?     1670           
  Lines                     ?   427108           
  Branches                  ?     5079           
=================================================
  Hits                      ?     9529           
  Misses                    ?   417495           
  Partials                  ?       84           

Flag	Coverage Δ
FmpDevicePkg	9.53% <ø> (?)
MdeModulePkg	1.65% <ø> (?)
MdePkg	5.44% <ø> (?)
NetworkPkg	0.55% <ø> (?)
PolicyServicePkg	30.42% <ø> (?)
SecurityPkg	1.56% <ø> (?)
StandaloneMmPkg	0.50% <ø> (?)
UefiCpuPkg	4.78% <ø> (?)
UnitTestFrameworkPkg	11.70% <ø> (?)

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[Michael Kubacki (makubacki)]

This would benefit from unit tests, but I don't think it's necessary given there are currently none in the plugin.

[Antaeus Kleinert-Strand (antklein)]

This would benefit from unit tests, but I don't think it's necessary given there are currently none in the plugin.

It was simple enough to add unit tests for __set_members. I modeled it after the DebugMacroCheckPlugin test design.