Move VisualStudioSymbolSearchService functionality to OOP

[tmat]

This service depends on NuGet VS APIs that only work on STA thread:

• IVsPackageInstallerServices. Removed in Move off of the legacy IVsPackageInstallerServices.IsPackageInstalled API. #53399
• IVsPackageInstaller2, IVsPackageUninstaller. Tracked by Add async implementation of IVS Package Installer/Uninstaller services NuGet/Home#8896 and https://devdiv.visualstudio.com/DevDiv/_workitems/edit/959448
• IVsPackageSourceProvider. Tracked by https://devdiv.visualstudio.com/DevDiv/_queries/edit/959453

We will need NuGet to provide IServiceBroker service that provides the required functionality.

[CyrusNajmabadi]

Ideally one that also doens't throw on values the caller cannot validate beforhand.