[ZEPPELIN-6077] Remove raw types for AngularObject

[Reamer]

What is this PR for?

This pull request removes the raw use of the AngularObject. The generic version has been removed. AngularObject now contains an object reference. As a result, warnings from the IDE due to raw use disappear. The code is also easier to read.

What type of PR is it?

• Refactoring

What is the Jira issue?

• https://issues.apache.org/jira/browse/ZEPPELIN-6077

How should this be tested?

• CI

Questions:

• Does the license files need to update? No
• Is there breaking changes for older versions? No
• Does this needs documentation? No