Change checkout actions to use newer restore syntax

[jat255]

This PR resolves #691 and changes all references to git checkout to either git restore (or git switch) as appropriate. I believe I got all the references, but a close look at the changes my a maintainer would be great. Since 2.28.0 is the default version in newer versions of Git for Windows and Linux, I think it makes sense to make these changes now. I've included the older syntax in comments in case people are using an older version, too.

I also tried to update the output blocks to reflect the verbiage used by git in more modern versions (I ran all the examples with Git 2.28.0 on Linux).

[kekoziar]

Hi, @jat255. Thanks for working on the needed change that updates the listed output. However, please remove the changes to the identifiers and dates. Also, I don't think exposition to differences between git versions is needed (nor usually incorporated in the lesson). Items like i/w and mnemonicPrefix were never introduced into the lesson, and are out of scope.

I do appreciate the changes from checkout to restore and directory to tree

[matuskalas]

I think the time is now very due to finally retire checkout from the lessons, and replace with restore and switch. 😊

[kekoziar]

I'm going to close this PR in preparation of the new workbench lesson infrastructure, but with the following points which halted the original merging of this PR.

Yes, the output text has changed so this can be updated; however, the original PR has many conflicts which need to be resolved, which halted being able to update and merge.

This content should be updated, at least during the next lesson content review, if not earlier.