Add File::Delete and File::DeleteDir warning flags

[Dentomologist]

Adds a flag to File::Delete and File::DeleteDir dictating whether they emit console warnings when the specified path doesn't exist. The flags are true by default to maintain existing behavior.

Also modifies the return value of DeleteDir when attempting to delete a nonexistent path to better reflect the intention of the function (nothing's there after the call). This change doesn't break anything because none of the existing callers actually check the return value.

Adds tests for Delete and DeleteDir.

[lioncash]

I don't think a bool is particularly useful visually here, because

File::Delete(path, false); doesn't really communicate intent particularly well. Maybe consider using an enum class instead.

[Dentomologist]

I don't think a bool is particularly useful visually here, because

File::Delete(path, false); doesn't really communicate intent particularly well. Maybe consider using an enum class instead.

I considered that but was reluctant to add an enum class that was only used by two function parameters. If you feel that's a better route I can go ahead and do that.

[lioncash]

Please do. It's much better to be noisily informed about behavior/intent, than not being informed about it at all.

[Dentomologist]

Noted! I've added the enum class as requested.

[Dentomologist]

I refactored a few things in the unit tests so that could use another look. In addition to renaming the path variables to use the m_ prefix I also separated assertions into separate functions. This is intended make it clearer exactly what is being tested, and also that the results of the delete shouldn't depend on the value of the IfAbsentBehavior.

[Dentomologist]

Added suggested changes by @leoetlino