[Rust] Fix undefined behaviour and and remove unsafe #24044
Description
The rust implementation contains a lot more unsafe than is necessary and in many of these instances it is possible to invoke undefined behaviour from safe code.
Reporter: Markus Westerlind / @Marwes
Assignee: Markus Westerlind / @Marwes
PRs and other links:
Note: This issue was originally created as ARROW-7813. Please see the migration documentation for further details.