chore!: Update aes-gcm to 0.10.3 and aes to 0.8.4

[kevaundray]

Description

This PR updates aes-gcm and is related to #260

Notes & open questions

Change checklist

• [ ] Self-review
• [ ] Documentation updates if relevant
• [ ] Tests if relevant

[kevaundray]

The clippy errors are orthogonal to this PR -- have fixed them in: https://github.com/sigp/discv5/pull/262