LSP: Support for custom hashing algorithm in F# workspace

We need hashing to compare different versions of files and projects in the workspace. FCS only has access to netstandard2.0 BCL which doesn't offer much so now it uses MD5. LSP and new VS extension can target any net8+ so can utilize `System.IO.Hashing` `xxHash`. We should make the hashing algorithm parametrizable in FSharpWorkspace so we can plug in this more performant one.