[V1] Plan cleanup and finalization

[RCHowell]

Description

This is a tracking issue for plan cleanup efforts and finalization, see #1665

Tasks

• [x] Convert interfaces to Java
• [x] Make full tree since we have the Operator interface now.
• [x] Remove default methods
• [x] Update RelScan input name
• [ ] Rewriter
• [ ] Copy
• [ ] Builder/factory updates

[RCHowell]

need rebase on #1658