Update ProjectSystemCache to be case insensitive for _primaryCache

[jgonz120]

Bug

Fixes: https://github.com/NuGet/Client.Engineering/issues/2829

Description

Projects information was being added/updated with different cases, causes our apex tests to fail. The primary key for the _primaryCache is projectNames.FullName which is the full path and filename of the project. Switching the dictionary to ignore case allows the project to be added to the single entry instead of creating a new one.

When we load an empty solution, there are no projects, and VsSolutionManager.EnsureNuGetAndVsProjectAdapterCacheAsync does not initialize the cache.

When we create a new project we call VsSolutionManager.OnEnvDTEProjectAdded which attempts to initialize the cache again then add the project.

EnsureNuGetAndVsProjectAdapterCacheAsync gets the project name from

NuGet.Client/src/NuGet.Clients/NuGet.VisualStudio.Common/IDE/VsHierarchyUtility.cs

Lines 37 to 43 in 0bf00d2

	public static string GetProjectPathForWebsiteProject(IVsHierarchy project)
	{
	Assumes.Present(project);
	ThreadHelper.ThrowIfNotOnUIThread();
	project.GetCanonicalName((uint)VSConstants.VSITEMID.Root, out string projectPath);
	return projectPath;
	}

Then later in OnEnVDTEProjectedAdded we get the full name from the EnvDTE.Project full name

NuGet.Client/src/NuGet.Clients/NuGet.VisualStudio.Common/ProjectSystems/ProjectNames.cs

Line 92 in 0bf00d2

string fullname = dteProject.FullName;

PR Checklist

• Meaningful title, helpful description and a linked NuGet/Home issue
• Added tests
• Link to an issue or pull request to update docs if this PR changes settings, environment variables, new feature, etc.

[jgonz120]

This was originally comparing ProjectNames. 3d091da#diff-5a34d358c305cf4b9fb65e2fba45c849406b2898a65aa0a75513e41370c2161aR19

ProjectNames.Equals does a case insensitive check over the full name, so this change restores the dictionary to be case insensitive.