Re-add coverage param to phpunit test

This also makes changes:

* Remove `make test-phpunit`, it is a part of `make validate`
* Use ubuntu 16.04 so we have phpdbg 7.0 available
* More verbosity.

Author: kabalin

.github/workflows/test.yml

@@ -30,7 +30,7 @@ jobs:
   citest:
     name: CI test
     needs: selftest
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-16.04
 
     services:
       postgres:
@@ -101,7 +101,6 @@ jobs:
       env:
         MOODLE_BRANCH: ${{ matrix.moodle-branch }}
       run: |
-        make test-phpunit
         moodle-plugin-ci phplint
         moodle-plugin-ci phpcpd
         moodle-plugin-ci phpmd
@@ -114,6 +113,6 @@ jobs:
             "$MOODLE_BRANCH" != 'MOODLE_310_STABLE' -a \
             "$MOODLE_BRANCH" != 'MOODLE_39_STABLE' ]
         moodle-plugin-ci phpdoc
-        moodle-plugin-ci phpunit
+        moodle-plugin-ci phpunit --verbose --coverage-text
         moodle-plugin-ci behat --profile default
         moodle-plugin-ci behat --profile chrome

Makefile

@@ -13,12 +13,13 @@ test-fixer: build/php-cs-fixer.phar
 
 .PHONY:test-phpunit
 test-phpunit: vendor/autoload.php
-	$(PHPUNIT)
+	$(PHPUNIT) --verbose
 
 .PHONY:validate
 validate: build/php-cs-fixer.phar vendor/autoload.php psalm check-docs
 	$(FIXER) fix --dry-run --stop-on-violation
 	$(COMPOSER) validate
+	phpdbg --version
 	phpdbg -d memory_limit=-1 -qrr $(PHPUNIT) --coverage-text
 
 .PHONY:psalm