Provide an in-process agent for both .NET Framework and .NET 8.0 #1726
Description
This would be a pluggable agent for use in running tests in-process.
It would target both runtimes for which the console runner is built.
It would be bundled as a dependency with both console runners.
This agent would have a key difference from other pluggable agents. The agent and launcher both target the same runtime and would be in a single assembly. The launcher would simply return a reference to the agent without actually "launching" anything.
In the case of the .NET 4.6.2 build, we would restore the --inprocess option. The option would give an error if the correct runtime were not installed.
In the case of the .NET 8.0 build, the agent would always be used, since that runner only supports inprocess execution right now. Existing inprocess execution code would be removed as would the reference to nunit.agent.core.
Of course, should we later decide to support out of process execution in the .NET 8.0 agent, we could change the implementation to work just as it does in .NET 4.6.2.
@nunit/engine-team @nunit/core-team Thoughts?