frontend: Improve UX around recording paths

[Warchamp7]

Description

Better approach to trying to solve the underlying issue I was working towards in #10974

• Prompts to create the configured recording path folder if it does not exist
• Attempting to save a screenshot to an invalid recording path no longer erroneously says the screenshot was saved
• Display error when attempt to Show Recordings with an invalid path

Motivation and Context

I want to smooth out problems for users with bad recording directories.

How Has This Been Tested?

Started recordings, replay buffers and screenshots with a valid recording path, an invalid one in a valid parent directory, and with an invalid path to a non-existent drive.

Types of changes

• Bug fix (non-breaking change which fixes an issue)

• Tweak (non-breaking change to improve existing functionality)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.

[PatTheMav]

Suggested change

	bool success = false;
	bool isScreenshotSaved = false;

Success by itself is ambiguous - did it successfully render the texture? Generate the image data? Store it to disk?

The only way to understand this is to go backwards from the Basic.StatusBar.ScreenshotSavedTo string being generated upon success but parsing the code that far shouldn't be necessary.

[PatTheMav]

Suggested change

	bool OBSBasic::promptCreateOutputPath()
	bool OBSBasic::ensureOutputPathExists()

It's probably irrelevant to the calling code how this is ensured, but it only cares that it is ensured.

[Warchamp7]

It's not ensured in this case since the user could click no. Would that still be appropriate here?

[PatTheMav]

IMO it's fine if the function that is supposed to ensure this path exists tells you it "couldn't do it", because then you know it wasn't able to fulfil its job. It also makes sense that the code will not continue, because a precondition isn't true.