[Rust] Simplify `MutableBuffer::write` and `MutableBuffer::write_bytes`

[asfimport]

Reporter: Jorge Leitão / @jorgecarleitao
Assignee: Jorge Leitão / @jorgecarleitao

PRs and other links:

• GitHub Pull Request #8645

_{Note: This issue was originally created as ARROW-10561. Please see the migration documentation for further details.}

[asfimport]

Jorge Leitão / @jorgecarleitao:
Issue resolved by pull request 8645
#8645