[Story] Require acknowledgement to send to a verified user if a device is unverified

[pixlwave]

Description

• As a user
• I want to be informed when a verified user has an unverified device on their account
• So that I know that our conversations aren't being intercepted.

Figma: iOS/Android

Acceptance criteria

• Sending a message to a verified user that has an unverified device on their account fails.
• An alert is shown when interacting with the failed message.
• The user can opt to not worry about that particular unverified device and send messages to this user anyway.

Size estimate

None

Dependencies

• None

Out of scope

• Nothing

Open questions

### Questions

Subtasks

### Android
- [ ] https://github.com/element-hq/element-x-android/issues/3301

### iOS
- [ ] https://github.com/element-hq/element-x-ios/issues/3160

### Rust
- [ ] https://github.com/matrix-org/matrix-rust-sdk/issues/3837
- [ ] https://github.com/matrix-org/matrix-rust-sdk/issues/3838
- [ ] https://github.com/matrix-org/matrix-rust-sdk/issues/3973

### Crypto
- [ ] https://github.com/matrix-org/matrix-rust-sdk/issues/3792

[richvdh]

I believe this issue only tracks the work for Element X. Have opened https://github.com/element-hq/element-web/issues/27943 to add it to element-web.