Allow hiding invite messages from timeline

[RavuAlHemio]

Checklist

• Tests written for new code (and old code if feasible).
• New or updated public/exported symbols have accurate TSDoc documentation.
• Linter and other CI checks pass. -- PR requires approval from maintainer to run CI checks
• I have licensed the changes to Element by completing the Contributor License Agreement (CLA)

[dbkr]

Thanks for your PR! Here's the next steps to getting this merged:

• Product signoff: we'll need to decide whether this is a thing we're willing to support in the product. Making an enhancement issue would help for this as the template will give you prompts for the necessary information.
• Tests

[RavuAlHemio]

#28252 is the requested enhancement issue; tests are a work in progress.

[RavuAlHemio]

I have added relevant tests. They might be brittle if invites become summarized in the future, though...

[langleyd]

I've discussed this with product and it is not a setting we are looking to add at the moment. If anything we would like to have less settings in future. We will however look to improve the timeline experience such that less of them are needed.