Unskip some tests, delete others (#1742)

Clean up a bit the testsuite and integration tests.
Highlights:

- Some of the @skipped tests just worked -- I unskipped them
- some worked after some small tweak to adapt to the new pyscript next
- some are still skipped, but I tweaked the skip message to be more precise and descriptive
- Moreover, I killed/removed the ones which no longer make sense in the context of pyscript next; in particular, I removed all the ones which tested Element (which is now gone) and the one which tested py-config features which are no longer needed (e.g., multiple interpreters).

The testsuite passes locally.

pyscript.core/tests/integration/test_01_basic.py

@@ -167,7 +167,6 @@ class TestBasic(PyScriptTest):
                                                "C true false",
                                                "D <div></div>"]
 
-    @pytest.mark.skip(reason="FIX TEST: Works on CHROME")
     def test_packages(self):
         self.pyscript_run(
             """
@@ -188,8 +187,6 @@ class TestBasic(PyScriptTest):
             "hello asciitree",  # printed by us
         ]
 
-    # TODO: if there's no <script type="py"> there are surely no plugins neither
-    #       this test must be discussed or rewritten to make sense now
     @pytest.mark.skip("FIXME: No banner")
     def test_non_existent_package(self):
         self.pyscript_run(
@@ -197,6 +194,9 @@ class TestBasic(PyScriptTest):
             <py-config>
                 packages = ["i-dont-exist"]
             </py-config>
+            <script type="py">
+                print('hello')
+            </script>
             """,
             wait_for_pyscript=False,
         )
@@ -211,8 +211,6 @@ class TestBasic(PyScriptTest):
         assert expected_alert_banner_msg in alert_banner.inner_text()
         self.check_py_errors("Can't fetch metadata for 'i-dont-exist'")
 
-    # TODO: if there's no <script type="py"> there are surely no plugins neither
-    #       this test must be discussed or rewritten to make sense now
     @pytest.mark.skip("FIXME: No banner")
     def test_no_python_wheel(self):
         self.pyscript_run(
@@ -220,6 +218,9 @@ class TestBasic(PyScriptTest):
             <py-config>
                 packages = ["opsdroid"]
             </py-config>
+            <script type="py">
+                print('hello')
+            </script>
             """,
             wait_for_pyscript=False,
         )
@@ -350,7 +351,6 @@ class TestBasic(PyScriptTest):
         assert script_py_tag.evaluate("node => node.srcCode") == 'print("hello from script py")'
 
 
-    @pytest.mark.skip(reason="FIX TEST: works in chrome!")
     def test_py_attribute_without_id(self):
         self.pyscript_run(
             """