[16.0] component_event: fix test base class

[simahawk]

There's no reason for these tests to depend on BaseCase but we cannot depend on unittest.TestCase
because Odoo's test suite runner expects to find some attributes on the test class which come from BaseCase.

 Traceback (most recent call last):
  File "/opt/odoo/odoo/service/server.py", line 1299, in preload_registries
    registry = Registry.new(dbname, update_module=update_module)
  File "<decorator-gen-14>", line 2, in new
  File "/opt/odoo/odoo/tools/func.py", line 87, in locked
    return func(inst, *args, **kwargs)
  File "/opt/odoo/odoo/modules/registry.py", line 90, in new
    odoo.modules.load_modules(registry, force_demo, status, update_module)
  File "/opt/odoo/odoo/modules/loading.py", line 487, in load_modules
    processed_modules += load_marked_modules(cr, graph,
  File "/opt/odoo/odoo/modules/loading.py", line 371, in load_marked_modules
    loaded, processed = load_module_graph(
  File "/opt/odoo/odoo/modules/loading.py", line 281, in load_module_graph
    suite = loader.make_suite([module_name], 'at_install')
  File "/opt/odoo/odoo/tests/loader.py", line 55, in make_suite
    return OdooSuite(sorted(tests, key=lambda t: t.test_sequence))
  File "/opt/odoo/odoo/tests/loader.py", line 53, in <genexpr>
    if position_tag.check(t) and config_tags.check(t)
  File "/opt/odoo/odoo/tests/tag_selector.py", line 54, in check
    test_module = test.test_module
``

[simahawk]

Dammit, seems related to this big refactoring merged yesterday 😭
odoo/odoo@9a5d1ea

[simahawk]

This change is not needed if they accept my fix here odoo/odoo#114007