Avoid enumerator boxing for ItemBucket

[Erarndt]

Fixes #

The ItemBucket constructor enumerates some dictionary keys through the ICollection interface that causes allocations by boxing an enumerator.

Context

The only type that's passed to the constructor is a dictionary and we pass the associated KeyCollection which ends up getting boxed. We can just pass the concrete type to avoid this.

Changes Made

Testing

Notes

[Copilot]

Pull Request Overview

This PR aims to improve performance by avoiding enumerator boxing when iterating over dictionary keys for the ItemBucket constructor.

• Updated the ItemBucket constructor parameter type to use Dictionary’s KeyCollection directly.
• Adjusted unit tests to pass the concrete KeyCollection.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/Build/BackEnd/Components/RequestBuilder/ItemBucket.cs	Changed parameter type to avoid enumerator boxing for performance.
src/Build.UnitTests/BackEnd/TaskExecutionHost_Tests.cs	Updated test initialization to match the new constructor parameter type.

Comments suppressed due to low confidence (1)

src/Build/BackEnd/Components/RequestBuilder/ItemBucket.cs:77

• While the change improves performance by avoiding boxing, ensure that exposing the concrete KeyCollection type fits within the long-term API design, as it may limit flexibility if future needs require a broader abstraction.

Dictionary<string, ICollection<ProjectItemInstance>>.KeyCollection itemNames, // PERF: directly use the KeyCollection to avoid boxing the enumerator.