Convert web tests to browser tests for telephone module

let's do it.
Thanks!

+1

Committed and pushed bd27a538efe033eb2218da40c9544d648fc91984 to 8.2.x and a266f04 to 8.1.x. Thanks!

Added to both branches because out of sync tests are a pain.

This issue introduced a random fail similar to #2776269: High random fail rate in BTB forum tests on Postgres (especially, but not only, with PHP7) but at a lower rate. E.g. see:
https://www.drupal.org/pift-ci-job/397411

Telephone.Drupal\Tests\telephone\Functional\TelephoneFieldTest
✗	
testTelephoneField
fail: [Other] Line 47 of core/modules/telephone/tests/src/Functional/TelephoneFieldTest.php:
Drupal\Tests\telephone\Functional\TelephoneFieldTest::testTelephoneField
Behat\Mink\Exception\ExpectationException: The string "" was not found anywhere in the HTML response of the current page.

/var/www/html/vendor/behat/mink/src/WebAssert.php:770
/var/www/html/vendor/behat/mink/src/WebAssert.php:325
/var/www/html/core/tests/Drupal/FunctionalTests/AssertLegacyTrait.php:188
/var/www/html/core/modules/telephone/tests/src/Functional/TelephoneFieldTest.php:90
✗	
rupal\Tests\telephone\Functional\TelephoneFieldTe
fail: [Other] Line 0 of sites/default/files/simpletest/phpunit-1700.xml:
PHPunit Test failed to complete
✗	
nkno
fail: [run-tests.sh check] Line 0 of :
FATAL Drupal\Tests\telephone\Functional\TelephoneFieldTest: test runner returned a non-zero error code (2).

Postponing as per #2737805-32: Convert web tests to browser tests for forum module. :(

We figured out the reason, let's get back on track, see #2776269: High random fail rate in BTB forum tests on Postgres (especially, but not only, with PHP7)

Back to RTBC

We still haven't decided how we're going to do this - see #2735005: Convert all Simpletest web tests to BrowserTestBase (or UnitTestBase/KernelTestBase)