feat: Add ability to check events that are type annotated

[bmtcril]

Description:

Currently adding a type annotation to an openedx-events definition causes the linter to crash astroid:

  File "/home/ty/Dev/edx-lint/edx_lint/pylint/events_annotation/events_annotation_check.py", line 154, in visit_call
    if self._is_annotation_missing_or_incorrect(node):
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/ty/Dev/edx-lint/edx_lint/pylint/events_annotation/events_annotation_check.py", line 211, in _is_annotation_missing_or_incorrect
    node_event_name = node.parent.targets[0].name
                      ^^^^^^^^^^^^^^^^^^^
AttributeError: 'AnnAssign' object has no attribute 'targets'. Did you mean: 'target'?

This fix handles the use case of:

TRACKING_EVENT_EMITTED: OpenEdxPublicSignal = OpenEdxPublicSignal(
    event_type="org.openedx.analytics.tracking.event.emitted.v1",
    data={
        "tracking_log": TrackingLogData,
    },
)

as well as some linting issues in that file.

Merge checklist:

• All reviewers approved
• CI build is green
• If adding new checks, followed how_tos/0001-adding-new-checks.rst
• Changelog record added (if needed)
• Documentation updated (not only docstrings) (if needed)
• Commits are squashed