Ensure Console.Out is not disposed and is restored if it was replaced during the test run

[normj]

I'm on the AWS .NET team. We got a report from a user that used NUnitLite and got an object disposed exception when using this library in their AWS Lambda functions. Lambda is AWS's serverless compute offering.

In Lambda we redirect Console.Out to our own StreamWriter for logging. NUnitLite is wrapping Console.Out with its own ColorConsoleWriter and when it is done it disposes ColorConsoleWriter and disposes its inner TextWriter which would normally be the console stdout that ignores the dispose call but instead calls our TextWriter to dispose. With our TextWriter disposed any calls to Console.Out now fail.

We have fixed Lambda to ignore the dispose call but I though this PR would be helpful for others to ensure NUnitLite doesn't accidently dispose of somebody else's custom Console.Out.

I also made sure if Console.SetOut or Console.SetError are used to be sure to restore to the original TextWriters after the run is complete.

Fixes #4319

[OsirisTerje]

1. @normj Would be nice to see a test around this.
2. @stevenaw @normj Should this also be backported to 3.13 ?

[stevenaw]

I think this could be helpful for 3.13. Redirecting or splitting these outputs has been a bit of a common request in issues and discussions the last few months.

[OsirisTerje]

@normj Would you mind creating another PR for merging into the https://github.com/nunit/nunit/tree/v3.13-dev branch?

[normj]

🤦‍♂️ Not adding tests on a PR for a test framework

@OsirisTerje I added a test to cover the ColorConsoleWriter. I made sure the test failed without this PRs code changes for ColorConsoleWriter. I'm not sure how to add a test for the change in the Execute method of TestRunner since that is the code executing the tests. Appreciate any suggestions there.

I'm happy to make a make a backporting PR to the v3.13-dev branch once I know I got this PR right.

[OsirisTerje]

Looks like everything is in order. Thanks @normj for the contribution!