[C++][Java][Format] Support Decimal256 Type

[asfimport]

Reporter: Micah Kornfield / @emkornfield
Assignee: Micah Kornfield / @emkornfield

PRs and other links:

• GitHub Pull Request #8475

_{Note: This issue was originally created as ARROW-9747. Please see the migration documentation for further details.}

[asfimport]

Micah Kornfield / @emkornfield:
Issue resolved by pull request 8475
#8475