Global configuration flag for media previews

[Half-Shot]

This implements MSC4155
Figma

This feature adds support for an account-level setting for configuring your own safety levels when browsing rooms. We already have support for configuring media previews on a per-device level but this allows the configuration to be expressed cross-device / client.

While not explicitly implemented, this also allows for servers to express defaults for their users (by setting default account data, if the server supports it).

Global setting

Room setting

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.
• I have licensed the changes to Element by completing the Contributor License Agreement (CLA)

[amshakal]

Looks fine to me but the spacing seems a bit off between:

1. The title and subheading in 'Show media in timeline' section
2. The spacing between different radio button options

[Half-Shot]

Looks fine to me but the spacing seems a bit off between:

1. The title and subheading in 'Show media in timeline' section

2. The spacing between different radio button options

How's this @amshakal ?

[amshakal]

That's better! :) TY!