Potentially remove the `unsafe` markings from unchecked functions

[HyperCodec]

The unsafe keyword is primarily reserved for UB. Because these functions don't cause UB, but rather just really difficult-to-trace errors, the terminology could be confusing despite having docs saying it's not UB.

[HyperCodec]

I could also probably extract it to a separate trait, which must be explicitly imported in order to call these methods.

[HyperCodec]

Will probably implement this in the same PR as #94 because they kind of go hand-in-hand (both related to improving debugging experience).

Edit: Too lazy to do this issue rn, will do separate PR.