get_block_template filter not fired when template saved in posts

[ianmjones]

The \get_block_template() function fires a 'get_block_template' filter at the end that allows for plugins to filter the content etc.

However, this only works if the template was retrieved from a theme's template file, if the template has been edited it is saved into the posts table.

When a template (part) is found in the posts table the function exits early with the found template but does not wrap the return in a call to the 'get_block_template'.

This means plugins and custom code do not get a chance to filter the template's content or properties when re-editing after a template has had an initial edit.

[ianmjones]

Simple patch.