Microsoft.Extensions.DependencyInjection.ServiceLookup.ServiceCacheKey
Type of service being cached
Reverse index of the service when resolved in IEnumerable<Type> where default instance gets slot 0.
For example for service collection
IService Impl1
IService Impl2
IService Impl3
We would get the following cache keys:
Impl1 2
Impl2 1
Impl3 0
Indicates whether the current instance is equal to another instance of the same type.