Remove MakeGenericMethod from the query hot path

[roji]

When calling terminating operators such as Single, Average, we currently call MakeGenericMethod, which is slow; when running a basic tracking query + update against InMemory, this (and the related GetGenericArguments) take up around 0.6% of the running time with Npgsql, around 6% with InMemory.

We could probably follow the runtime's pattern to get rid of this.

[ranma42]

The links are now outdated.
The EFCore link is

efcore/src/EFCore/Extensions/EntityFrameworkQueryableExtensions.cs

Line 3076 in 231565f

: operatorMethodInfo.MakeGenericMethod(typeof(TSource));

The runtime link is https://github.com/dotnet/runtime/blob/215b39abf947da7a40b0cb137eab4bceb24ad3e3/src/libraries/System.Linq.Queryable/src/System/Linq/Queryable.cs#L772