Better strategy for fixing ASP.NET core runtime pack restoring

Currently, we use a hack where we invoke nuget.exe directly to install the Microsoft.AspNetCore.App.Runtime.linux-arm64 package.

This package is necessary in order to build our project for arm64-v8a with ASP.NET core, however due to some quirks with the net6.0-android target, it won't restore it automatically.

Invoking nuget manually isn't ideal as it requires nuget.exe to be available on PATH (which is not the case in a standard installation of .NET 6, as it only includes the necessary DLLs for restoring nuget packages with msbuild).