This is part of issue #909.

IAgentLauncher will be the new extension interface for pluggable agents. It also introduces the struct TestAgentInfo, which gives information about each agent. Additional interfaces may also be needed. The first cut of the interface will be taken from that used in TestCentric and we'll develop it further from there.

Initially, IAgentInfo will be used internally only. A launcher will be created for each built-in agent. This is intended to facilitate converting agents, one by one, to pluggable extensions. Once that is complete, the code for loading these internal engines will be removed.

UPDATE

Having implemented all of the above in a PR, I realized that very little change is needed to go a great deal further and I have renamed this issue accordingly.

Both of the existing agents (net462 and net8.0) will be converted to pluggable agents. They will be packaged and published as extensions and NUnit.ConsoleRUnner will include them as dependencies.

For the moment, they will continue to be built as a part of the console project. Creation of separate project repositories for each of them will then be a separate step and mostly a set of mechanical changes.