[6.x] Change shouldBootRootItems visibility in AddonServiceProvider

[marcorieser]

This PR changes shouldBootRootItems visibility from private to protected, so inheriting classes can use it.

For example, I want to overwrite the logic of how my addon config is published and still prevent multiple boots by calling this from within the overwritten bootConfig() method:

protected function bootConfig()
{
    if (! $this->shouldBootRootItems()) {
        return $this;
    }

[jasonvarga]

What would you be changing?

[marcorieser]

I want to publish to a directory in the config folder.

[marcorieser]

Just realized that shouldBootRootItems() calls other private methods and accesses a private property. This needs a bit more thinking I guess.

[jasonvarga]

I'll close this for the moment, but if you can show a full example of what you plan to do, we can revisit it.

Changing a private method to protected means we need to think about how people would be overriding etc.