Break out a helper class from GenerateVisitor annotation processor.

[MMcM]

This allows service loading all annotation processors and even determining that this one does not apply, without having javapoet in the classpath.

[foundationdb-ci]

Result of fdb-record-layer-pr on Linux CentOS 7

• Commit ID: 92e5ae6
• Duration 0:54:55
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)

[foundationdb-ci]

Result of fdb-record-layer-pr on Linux CentOS 7

• Commit ID: 8f66a20
• Duration 0:54:04
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Log terminal output (available for 30 days)
• Build Workspace zip file of the working directory (available for 30 days)