Add tests for EFCore.Tasks

[AndriySvyryd]

These tests would need to do the following:

1. Set up one or more target projects
   a. The task binaries and content files need to be explicitly laid out and referenced, since there is no NuGet package yet when the tests run
2. Run a dotnet command on one of the above
3. Assert on the command output and the artifacts of the target project

Features to test:

1. MsBuild integration for compiled model and precompiled query generation for Build and Publish
2. NativeAOT
3. Trimming
4. Feature flags

Related to #32616
Also see https://github.com/dotnet/efcore/blob/main/eng/testing/linker/trimmingTests.targets