Add Changed event to TestPackage

[CharliePoole]

Currently, the runner TestCentricProject class inherits from TestPackage and implements an IsDirty property used to determine whether the project needs to be saved. The implementation is somewhat flawed because not all changes made to the base class are observable. Moving the property to TestPackage itself will simplify the runner's job and be more reliable. In addition, it will give us a single implementation accessible to all runners.

UPDATE: After some exploration, it seems cleaner to implement a Changed event which TestCentricProject can override.

It's possible that some other aspects of the TestCentricProject class will also need to be moved to the engine API. We'll examine that as part of this issue.

[CharliePoole]

🎉 This issue has been resolved in version 2.0.0-beta6 🎉

The release is available on:

• GitHub Release
• NuGet Package