Update the default file carver block size to be compatible with MySQL 8
& S3.
Update surrounding docs.
Various other updates to references of MySQL versions (all terraform
deploys are now defaulted MySQL 8 in AWS)
# Checklist for submitter
If some of the following don't apply, delete the relevant line.
- [X] Changes file added for user-visible changes in `changes/` or
`orbit/changes/`.
This matches the default identifier used in Fleet's prior recommended
osquery installation, easing migration for users. It can still be
overridden via a flagfile.
