Make webform blocks (block.webform.block:*) fully validatable so they can be used in Experience Builder

Added steps to reproduce with screenshot from config inspector and guidance on where to find compatibility checking in XB.

Looked a bit at this with Gábor.

This will be the first step to make Webforms XB compatible, but not enough. I'd suggest we keep the scope here to make it FullyValidatable.

The bad news, as this uses a yaml blob in its config, a custom xb transform will be needed for the widget.
The good news, parts of this aparently was done already in WebformTranslationConfigManager for compatibility with config translations form integration.

Added 📌 Add xb transform to webform block storage so that it works with Experience Builder Active for that, so we can keep scope there.

Thanks for looking into this! Tested the MR. The webform block I created is almost validatable now :) The provider and webform block ID seems to have errors still in config inspector:

I don't know if this block has all the keys that webform blocks have all the time, but if it does, then solving these two would solve it for all webform blocks :)

I also looked at the component list in XB and it still says that it is not validateable indeed.

@penyaskito could you point me in the direction of a custom xb transform that has already been implemented?