UTD Hook | Add support for late decryption grace period for parity with Web

On web we have a configurable grace period for late key delivery
https://github.com/element-hq/element-web/blob/9a126795a81d13aba2d331b38df75878682d54a1/src/DecryptionFailureTracker.ts#L122

```typescript
/** If the event is successfully decrypted in less than 4s, we don't report. */
public static GRACE_PERIOD_MS = 4000;
```

There is no similar mecanism with the rust UTD hook, the late decryption are never graced
https://github.com/matrix-org/matrix-rust-sdk/blob/9b6de4e4367a465b7605eb931d0e4375df8f5ddd/crates/matrix-sdk-ui/src/unable_to_decrypt_hook.rs#L268-L283

Start with crates/matrix-sdk-ui/src/unable_to_decrypt_hook.rs around lines 268-283, then compare the referenced DecryptionFailureTracker.ts grace-period behavior in element-web. Determine how late key delivery is handled by the UTD hook and define completion as late decryptions within the configured grace period no longer being reported.

Written by the indexing model from the issue text.