Thrift services can be further decomposed

While working on #2620 there was a comment regarding how the Thrift services could be further decomposed. See https://github.com/apache/accumulo/pull/2620#issuecomment-1096592315.

Start by reading issue #2620 and the referenced comment on pull request #2620, which is the only stated context for decomposing the Thrift services. The issue does not identify files, tests, a specific decomposition, or completion criteria, so the required scope would need to be established before implementation.

Written by the indexing model from the issue text.