Copy full class name to clipboard (Java)

### Description

When you hover on tabs it would be nice to be able to copy full class name for currently open Java class. So package name and name of the class.


### Use case/motivation

We (in out team) use class names or full class names to share information on bug tracker, chat, review notes etc. Those names are then useful for navigation with `alt`+`shift`+`o` (Go to File).

Note that file paths are less useful because we all have different paths to projects. So at least for Java full names are better. For other projects we share and use relative paths sometimes (relative to project root).

### Related issues

_No response_

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

Yes

The issue names no files, tests, or entry points. Start by locating the Java editor tab hover behavior and the existing copy or context-menu actions; done means a currently open Java class can copy its package-qualified class name for use in navigation and notes.

Written by the indexing model from the issue text.