impr: Enforce LMDB to read and write always with a prefix (FOR-137)

[jyeshe]

What

This is a more strict implementation of #427 that "Reject reads with invalid/missing prefixes".

Why

As such it satisfies all FOR-137 expected behaviour:

• All data values should be prefixed with data: when written
• All reads should validate the first 5 characters of the raw value (except for group)
• Parse prefix from binary string: data: or link:
• Reject reads with invalid/missing prefixes

Additional Notes

This PR is ready for review however it's on Draft once it can only be merged when a migration strategy is defined in regards to the existings caches without the prefix for data.
There will be no migration and the sync is part of the scope of a following task.

[jyeshe]

@twilson63 by enforcing the read to also to match a prefix, which demands existing values to be rewritten, you will notice it allows a lot of simplification on the code making it more readable.

[jyeshe]

@twilson63 FYI two details were discussed in the daily:

1. We should not provide a migrate function (users can easily rebuild the cache by themselves)
2. The sync was considered as part of the scope of a following task.

Should I work on the 2nd or do we have other priorities? cc @samcamwilliams
EDIT: The issue for the sync is this one https://linear.app/forward-research/issue/FOR-139/feat-add-sync-function-for-hb-store

[jyeshe]

Only a flaky failed.

      dev_router: dynamic_routing_by_performance...*failed*
in function hb_cache:report_ensure_loaded_not_found/3 (/Volumes/T7Shield/HyperBEAM_shield/src/hb_cache.erl, line 132)

Failed: 1. Skipped: 0. Passed: 1204.