Epic | No more gray/warning shields

There are several scenario that will currently creates key warnings on messages. This warning are mostly noise and distract users from potential important warning:

The assymetric backup is a big source of unsafe keys warning
- https://github.com/vector-im/element-meta/issues/747

Allow own trusted session to share the trust flag of keys, thus allowing such forwards to result in trusted keys
- https://github.com/vector-im/element-meta/issues/756

- \[ \] https://github.com/vector-im/element-meta/issues/763

- \[ \] Don't cancel outgoing key request until a safe key received.
- \[ \] Re-decrypt if needed when a safe key is updated to update shields

- \[ \] reshare outbound session as m.room.key and not forward

Start by reviewing the linked issues 747, 756, and 763, then map each checklist item to the relevant Element client work. The issue is complete only when the listed key-sharing, key-request, re-decryption, and outbound-session scenarios no longer produce unnecessary warning shields.

Written by the indexing model from the issue text.