Text overlay: introduce options to decode HTML entities and strip HTML tags from the overlaid text

Let's update the test too.

For understanding, can you please explain how you are getting to have HTML entities at this point of effect execution? Via tokens, programmatically, etc?

IMHO I think here we should be dealing with text only, with any HTML decoding/stripping done already in code upstream. If (edge case, I know) you want to actually have " overlaid on the text, then with this you would get it converted to " anyway.

For example, in Textimage, the content of a text field is passed through strip_tags before being sent to the image effect (see #2150599: Filter field text before using it to render a Textimage), so when the effect code is executed this actually manages a filtered and 'clean' text already.

Let's do #2702205: Text overlay: add an hook to alter the overlaid text and use it to enable setting maximum number of characters displayed first, then use the hook mechanism introduced there to do this, adding an option to the effect so that users can decide if to do the decoding or not.

Patch. Introduces UI options in the Text Overlay effect config form for:

• removing HTML tags
• decoding HTML entities

+ update functions + tests.

Force conversion to bool when getting the config value from the form.

Testing manually, there are schema issues when previewing the effect results.

Removed a PHP notice while previewing.

Committed.