add allow_html5 option to date and time FormType to disable HTML5 date input when widget is set to single_text

remove unnecessary test when creating datetime format data transformer
feature #8291 [Form] Add allow_html5 option to date and time FormType to disable HTML5 input type (csanquer)

This PR was merged into the 2.6-dev branch.

Discussion
----------

[Form] Add allow_html5 option to date and time FormType to disable HTML5 input type

[Form] added allow_html5 option to date and time FormType to disable HTML5 input type when widget is set to single_text

| Q                    | A
| --------------------- | ---
| Bug fix?          | no
| New feature?   | yes
| BC breaks?     | no
| Deprecations? | no
| Tests pass?    | yes
| Fixed tickets   | #6927 #7123
| License           | MIT
| Doc PR           |

With this little patch we can have a single text widget without HTML5 date input type which is required when using some javascript date or time picker .

Commits
-------

392d6c7 add allow_html5 option to date and time FormType to disable HTML5 date input when widget is set to single_text
fixed CS