Merge changes from dev-4.0 branch into main

[CharliePoole]

I'm making this an issue because it's not going to be an automatic process. I've done some experimentation and concluded that we will need to select changes manually and do them through PRs. That's because some we want to keep changes in dev-4.0 in some cases but overwrite them in other cases, where improved code has been added to the main branch. Essentially, I'm afraid we have kept the branches separate for too long.

Here is a list of outstanding changes generated by the command git cherry -v main dev-4.0:

• fd7c956 Remove RecentFilesService from Engine
• 8e72600 Set default version to 4.0.0
• d2157a3 Remove SettingsService
• c3ccd75 Update service-related tests
• 104dbca Update EngineApiVersion.cs
• 8f618c5 Remove property no longer in use
• 1c2a36a Drop NUnitConfiguration class
• 1be5b9d Drop DomainUsage options
• 4c34824 Refactor tests
• 7a5c852 Standardize TestPackage Construction
• b26897d Eliminate engine extension test for now
• d34be71 Changes from review
• 768403a Clean up comments
• 6299b26 Consider later NUnit versions as a valid framework.
• a7efe43 Add Tests for NUnit3DriverFactory.
• e288b82 Added required file header.
• 8d5c9a9 Publish merges to dev-4.0 to myget as dev builds
• cd6da16 Treat dev-4.0 same as master in build.cake

More detailed info is available using git rev-list dev-4.0 --not main -v

I'll use the above info to create individual tasks under this epic, many of which will be breaking changes.

[CharliePoole]

The following issues were closed upon merging to dev-4.0. I have re-opened them. Once they are done, the commits listed above should be re-checked to see if we need additional issues or PRs.

• Remove RecentFilesService from Engine #874
• Remove UserSettings From Engine #873
• Eliminate DomainUsage setting #860
• v4: Create single constructor method/structure for a TestPackage #889
• Consider later NUnit versions as a valid framework. #1041

[CharliePoole]

All sub-issues are ready to merge once 3.15 is released. I'll do PRs for each of them one at a time in the order listed, since they build on one another.

[CharliePoole]

All functionality from the dev-4.0 branch has been ported to main. I'll keep that branch around for a short while to make sure.