[Rust] implement extend for MutableBuffer (from iterator)

[asfimport]

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

PRs and other links:

• GitHub Pull Request #9235

_{Note: This issue was originally created as ARROW-11291. Please see the migration documentation for further details.}

[asfimport]

Andrew Lamb / @alamb:
Issue resolved by pull request 9235
#9235