Improve "See the logs for details" notices

**Is your feature request related to a problem? Please describe.**
As a user I'm frustrated when the bridge tells me to "See the logs for details".
As a hookshot admin I'm frustrated when users ask me to look for the logs.

**Describe the solution you'd like**
If we don't expect it to be confidential, include the error message in the notice.

**Describe alternatives you've considered**
Making errors in logs easier to find by adding a unique ID. See #268.

**Additional context**
Add any other context or screenshots about the feature request here.

**Instances**
https://github.com/matrix-org/matrix-hookshot/blob/75a91d0ab4a4285a38f59c07f3a5a3682021b38c/src/AdminRoom.ts#L220-L221

Start with the notice handling at src/AdminRoom.ts lines 220-221 and trace how its error information is produced. Update the notice behavior so non-confidential errors are included while confidential details remain in the logs, then verify the affected bridge notices and their wording.

Written by the indexing model from the issue text.