[Format] Add Opaque canonical extension type

[lidavidm]

Describe the enhancement requested

As proposed on the mailing list: https://lists.apache.org/thread/4pykofrzvkl7dwsnzys8rwnq2owfnt43

• [C++][Python] Add Opaque canonical extension type #43454
• [Go] Add Opaque canonical extension type #43455
• [Java] Add Opaque canonical extension type #43456

Component(s)

Format

[lidavidm]

Issue resolved by pull request 43457
#43457