Further reduce allocations in CreateGraphNodeAsync

[Erarndt]

Bug

Related: NuGet/Home#12748

Regression? Last working version:

Description

This PR makes additional changes to reduce allocations in CreateGraphNodeAsync() by addressing three issues highlighted in this trace:

A LightweightList was introduced in a previous PR to reduce the need to allocate a List<T> in the cases where the number of items was 4 or fewer. This value was chosen because it was seen as a safe starting point since it's the default size for List<T> as well as the 80th percentile in telemetry data

50 - 2,
70 - 3,
80 - 4
90 - 7
95 - 9

This trace indicates that there are still significant allocations occurring and this change allows LightweightList to contain up to 10 items before needing to allocate a List<T>.

The second change introduces a helper method on GraphNode that enables callers to ensure that InnerNodes has sufficient capacity to add additional items to minimize resizing.

Finally, FindRuntimeDependencies() often returns a List<T> wrapped by the IEnumerable<T> interface which was resulting in boxing of the List<T>.Enumerator. The existing NoAllocEnumerate() helper can be used here to avoid the boxing.

PR Checklist

• PR has a meaningful title

• PR has a linked issue.

• Described changes

• Tests

  • Automated tests added
  • OR
  • Test exception
  • OR
  • N/A

• Documentation

  • Documentation PR or issue filled
  • OR
  • N/A

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