[flatbuffers] Generated code can read and write out of bounds in safe code

Code generated by flatbuffers’ compiler is unsafe but not marked as such.
See https://github.com/google/flatbuffers/issues/6627 for details.

All users that use generated code by flatbuffers compiler are recommended to:

1. not expose flatbuffer generated code as part of their public APIs
2. audit their code and look for any usage of follow, push, or any method that uses them
   (e.g. self_follow).
3. Carefuly go through the crates’ documentation to understand which “safe” APIs are not
   intended to be used.

References

• https://github.com/google/flatbuffers/issues/6627
• https://rustsec.org/advisories/RUSTSEC-2021-0122.html
• https://github.com/google/flatbuffers/pull/7518
• https://github.com/google/flatbuffers/releases/tag/v22.9.29
• https://github.com/advisories/GHSA-3jch-9qgp-4844