Update dependencies on LSP branch (move to CLASP source package)

[abonie]

Examples of how new CLASP package is referenced in other projects:

Eg. razor - razor/src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/Microsoft.AspNetCore.Razor.LanguageServer.csproj at 6ada92f5fc25f916afccc41d3dce2c618d9fcd11 · dotnet/razor (github.com)
or webtools - https://devdiv.visualstudio.com/DevDiv/_git/VS?path=/src/Xaml/Designer/Source/CodeAnalysis/CodeAnalysis.csproj&version=GBmain&line=26&lineEnd=27&lineStartColumn=1&lineEndColumn=1&lineStyle=plain&_a=contents