[2.0.0-beta3] Sources: Tests

i take this one too

postponed to beta3

Hello,
i am still adding source tests in the MR, in progress ...
still missing tests for those sources :

BreadcrumbSource.php
ListTextareaWidget.php
MenuSource.php
NumberWidget.php
PathSource.php
SelectWidget.php
UrlWidget.php
WysiwygWidget.php

Also, in this MR :

- redistributed the tests between modules "ui_patterns_field_formatters" and "ui_patterns_latyouts"
- cleaned some files in tests, now unused
- update a component in test module "ui_pattterns_test"

finally... please review :)

a few items may be missing :

- Test of BreadcrumbSource
- Test of DerivableContext deriver