Stop using GetRequired* reflection wrappers to enable trimming

[roji]

This removes GetRequiredRuntimeMethod and similar wrappers (introduced during NRT annotation), since these are opaque to the linker when performing static analysis for trimming; the reflection APIs are called directly instead.

A console program is included as a regression test - to test it, execute dotnet publish -c Release -r linux-x64 --self-contained under test/EFCore.Trimming.Test and then attempt to run EFCore.Trimming.Test from the publish directory.

Assuming we want to add this to our CI pipeline, @smitpatel where would be the right place to add it? Just an additional step e.g. under Linux in azure-pipelines.yml?

Note #27098 which provides a hacky but much smaller fix for 6.0.

Fixes #26288

[smitpatel]

If it is not a test project, I would recommend updating azure-pipelines.yml to add additional step which runs this console app. You can also create batch file or sh file to build run it (so yml file will have single command invocation)