Make internal methods inaccessible

[schlessera]

WP-CLI exposes every public method it encounters in a command object as a new subcommand. Therefore we make the internal methods private again.

As this breaks the current tests, we add a helper function in the tests to invoke these private methods as if they were public. This is a short-term fix for now.

The cleaner long-term solution would be to work on #3077 and get all actual business logic out of the commands. When the commands do nothing more than parsing arguments and formatting outputs, these unit tests become unnecessary here.

Before

After

Fixes #3102

[kienstra]

Approved

Hi @schlessera,
Good idea to make these methods private.

Before

Like you mentioned, I also saw that these methods were listed as possible commands:

After

With this PR, methods aren't shown as commands:

And the existing commands still work as expected.

Like wp amp validation reset:

...and wp amp validation run: