Create unit tests for auto indentation

[DonJayamanne]

We've had a number of bugs & fixes related to auto-indentation.
We need to ensure we do not regress.

Create unit tests for the following rules:

    languages.setLanguageConfiguration(PYTHON.language!, {
        onEnterRules: [
            {
                beforeText: /^\s*(?:def|class|for|if|elif|else|while|try|with|finally|except|async)\b.*/,
                action: { indentAction: IndentAction.Indent }
            },
            {
                beforeText: /^\s*#.*/,
                afterText: /.+$/,
                action: { indentAction: IndentAction.None, appendText: '# ' }
            },
            {
                beforeText: /^\s+(continue|break|return)\b.*/,
                afterText: /\s+$/,
                action: { indentAction: IndentAction.Outdent }
            }
        ]
    });

[DonJayamanne]

Another issue #1461 that would need to be tested.

[luabud]

@DonJayamanne can we consider the cases in the description as fixed ? (#6939)

[DonJayamanne]

Not until, we have UI tests for this.