Small PR follow-ups

[jasonmalinowski]

Follow ups for #84948 (comment) and #84790 (comment)

Microsoft Reviewers: Open in CodeFlow

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Pull request overview

This pull request applies follow-up fixes for NuGet restore isolation and cached language-server project alias handling.

Changes:

• Clears inherited NuGet package-source mappings.
• Trims cached aliases and removes empty entries.

Show a summary per file

File	Description
src/Tools/BuildBoss/PackageInstallCheckerUtil.cs	Isolates generated NuGet mappings.
src/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/LanguageServerProjectSystem.cs	Normalizes cached aliases.

Review details

Suppressed comments (1)

src/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/HostWorkspace/LanguageServerProjectSystem.cs:245

• This fixes a cache-loading behavior change but adds no regression coverage for the normalization. The existing cache tests only assert the raw CachedMetadataReference aliases, while this GetAliases conversion is where empty and whitespace-only entries are removed; please add a language-server/cache-loading test that verifies inputs such as global, , Foo, produce exactly global and Foo.

                => item.Metadata["aliases"] is string aliases ? aliases.Split(',', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries) : [];

• Files reviewed: 2/2 changed files
• Comments generated: 0
• Review effort level: Lite