feat: Add priority for event handlers to Exiled Events

[louis1706]

Description

Describe the changes
Add priority for the eventhandler to the exiled events. This allows the plugin to be the last to handle an event even if the plugin has a high priority and vice versa.

What is the current behavior? (You can also link to an open issue here)
The current behaviour follow the order of ellements added in the inner event. First added first called.
First call the "classic" handler then coroutine handler.

What is the new behavior? (if this is a feature change)
First added first called, when same priority. highest priority, first call.
First call the "classic" handler then coroutine handler, when same priority.

Does this PR introduce a breaking change? no

Other information: I like trains
I didn't test it in game only in unit tests.
I don't care if this pull request get merge or not it's just a draft.
It took me 10 minutes to code it.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentations

Submission checklist

• I have checked the project can be compiled
• I have tested my changes and it worked as expected

Patches (if there are any changes related to Harmony patches)

• I have checked no IL patching errors in the console

Other

• Still requires more testing