gvfs-helper: move prefetch/since tracing to helper - #850

Found version-specific or distribution-specific runtime identifier(s): alpine-x64, win8-arm. Affected libraries: SQLitePCLRaw.lib.e_sqlite3.linux, SQLitePCLRaw.lib.e_sqlite3.v110_xp. In .NET 8.0 and higher, assets for version-specific and distribution-specific runtime identifiers will not be found by default. See https://aka.ms/dotnet/rid-usage for details.