Fix FuzzyCompareOGTerminalContainer and ConvertTo interfaces in OGTerminal

This PR involves:

* Changing the interface of `FuzzyCompareOGTerminalContainer` in `OGTerminal` so that no dangling references can be exposed, and `OGTerminal` no longer holds a reference to a `FuzzyCompareOGTerminalContainer` instance. This allows `FuzzyCompareOGTerminalContainer` to hold a `shared_ptr` instead of a `weak_ptr`, which will also prevent it from holding an expired pointer.
* Removing external access to the `ConvertTo` that has held by `OGTerminal`, as it is not needed externally, and would allow a dangling pointer. 

Coverage:

Java: 79%
build/src/jshim: 0.8%
build/src/librdag: 16.4%
src/jshim: 55%
src/librdag: 91.3%
src/librdag/runners: 95.7%

All unchanged except for src/librdag, which is down 0.1% because of the deletion of code that was covered.