Every form block now has unique ID (even the same block in two different form has different ID) used for rendering error messages. Before this, when the same form was rendered on a page multiple times, error messages of custom fields were always shown on the last rendered form, even if the first one was submitted.
[MAILPOET-6182]
The legend html was not escaped and was ignoring block settings coming
from the form editor.
This commit adds a new helper function for rendering legend that respects
applies block settings and also escapes the output.
[MAILPOET-4471]
