[UDP] Installing UDP package into project with Asset Store version of UDP will create conflicts

If an asset store version of the Universal Distribution Portal (UDP) is imported into a project, and then the package version of UDP is then after installed, this will introduce errors/conflicts such as:

PrecompiledAssemblyException: Multiple precompiled assemblies with the same name UDP.dll included for the current platform. Only one assembly with the same name is allowed per platform. Assembly paths: Assets/UDP/UDP.dll, C:/UDP Package vs Asset/Library/PackageCache/com.unity.purchasing.udp@1.1.2/Runtime/UDP.dll

Steps to reproduce:
- In Unity 2019.3, create a new project
- Window > Asset Store > Search "UDP" > Download and Import Universal Dsitribution Portal (UDP)
- Window > Package Manager > Install the Universal Distribution Portal (UDP) package
- Observe conflicts/errors between the 2 installations outputted to the console