Mac libvlc loading refactoring

[mfkl]

Description of Change

Refactoring the libvlc loading for both Xamarin.Mac (cocoa) and netcore on mac targets to allow loading a libvlc dynamic build, as opposed to the current static custom built libvlc.dylib package. This will allow to reuse the the official release builds, enabling us to do continuous delivery and will just work with libvlc 4 builds. This PR still needs a bit of work and cleanup but it is mostly working. It relies on a new libvlc.mac nuget though, that needs to be pushed and will be incompatible with previous libvlcsharp versions.

Issues Resolved

• fixes https://code.videolan.org/videolan/LibVLCSharp/-/issues/365

API Changes

None

Platforms Affected

macOS on both Mono and .NET Core runtimes.

PR Checklist

• [x] Rebased on top of the target branch at time of PR
• [x] Changes adhere to coding standard