Add individual token highlighting in Java for both read-only and mutable variables.

### Description

I'd like to be able to visually tell if a variable is read-only (final, or effective final), or mutable (because it gets assigned to), similar to how other IDEs support this.

### Use case/motivation

Motivation being that it greatly improves the sight-readability of code for those of that trained their eyes in this manner.

### Related issues

_No response_

### Are you willing to submit a pull request?

No

No files, tests, or editor entry points are named in the issue. Start by locating NetBeans' Java editor semantic-highlighting entry point and determine how it distinguishes final, effectively final, and assigned variables; done means read-only and mutable variables are visually distinguishable in both read-only and editable Java files.

Written by the indexing model from the issue text.