move lowest common ancestor of two ClassTypes into TypeHierarchy

[swissiety]

@wangzun66 unfortunately something in the RuntimejarConversionTest is failing. you can debug that faster down by adding a new testcase in that file that just executes the conversion of a single method - there should be another testcase as an example or at least in the git history of that file.

[wangzun66]

@wangzun66 unfortunately something in the RuntimejarConversionTest is failing. you can debug that faster down by adding a new testcase in that file that just executes the conversion of a single method - there should be another testcase as an example or at least in the git history of that file.

OK 👌