Convert QuickstartWeatherServer to file-based project and remove FileBasedMcpServer sample#1018

Copilot wants to merge 4 commits intomainmodelcontextprotocol/csharp-sdk:mainfrom

copilot/use-file-based-projects-in-samplesmodelcontextprotocol/csharp-sdk:copilot/use-file-based-projects-in-samplesCopy head branch name to clipboard