Update tests to use BrowserTestBase instead of WebTestBase

I did some digging into this, focusing just on one test and base, the tags test:

was:
isset($xpath[0][$xpath_value_attribute])
becomes:
null !== $xpath[0]->getAttribute($xpath_value_attribute)

was:
(string)$xpath[0]
becomes:
$xpath[0]->getText()

was:
$this->assertTrue($xpath[0][$xpath_value_attribute]);
becomes:
$this->assertTrue($xpath[0]->getAttribute($xpath_value_attribute));

The verbose() method doesn't work, and really throws up if you put the $xpath object in it, see issue.

Also some method names have changed:

assertEqual(): assertEquals(),
assertFalse(): assertEmpty(),
assertResponse: assertSession()->statusCodeEquals()

Basic move of the top level tests (so not the sub-module ones). Lets see where the test bot fails.

I've copied the base classes and @deprecated the simpletest versions. Currently just with a doc block tag, no trigger_error.

Didn't find any ajax/fake-js emulation in here, which is nice and hopefully leaves out the really complicated conversion stuff.

// Use the helper functions from the Functional trait. This is pretty safe but
// remember to rewrite all of these WebTestBase tests using BrowserTestBase
// before the next millenium.

:-)

this should clear up a fair number of fails.

Hmm not sure if MetatagPageManagerTest was ever run, since it was in the wrong namespace. Might fail now that it is in the right spot.

Moved all the sub-module tests that needed moving, didn't do more then a small sample test to see if they pass, so lets see what the bot makes of this.

124 pass in #16, 110 pass in #18, checked the jenkins logs and both times the same set of tests is detected, so not sure what is going on here.

edit:
Using Simpletest:
Drupal\metatag_twitter_cards\Tests\MetatagTwitterCardsTagsTe 50 passes

Using BrowserTestBase:
Drupal\Tests\metatag_twitter_cards\Functional\MetatagTwitter 2 passes

As far as I can tell, there are only 2 test cases in this test class, so seems to me that the PHPUnit count is right.

Patch applies cleanly 8.x-1.x, and converts all deprecated Simpletests to PHPUnit tests