Feature/netbeans 8230 reference count hints

[harshaindunil]

Summary

Implements a Java-editor-only reference count hint feature for methods and named types.

The editor shows an above-line reference count, opens a lightweight popup on click, and still allows opening the existing full Find Usages UI.

This is the initial Swing Java editor integration only. It does not attempt LSP or non-Java editor support.

Fixes #8230.

Main changes

• add Java reference count hint computation and publishing in java.editor
• add above-line block hint rendering support in editor.lib2
• add a completion-style usages popup from the hint click action
• reuse Java Where Used / Find Usages semantics for counts and navigation
• add Java inline-hints options for enabling reference counts
• add tests around direct reference counting and TreePathHandle resolution fallback

Performance / behavior notes

• counts are computed in background tasks
• counts are limited to visible declarations and refreshed as the viewport changes
• cached values are reused instead of clearing the full file on every index event
• existing hints remain visible while recomputation is deferred during scanning
• split editors for the same document are handled correctly

Validation

Manual validation in the built IDE:

• Java editor rendering of above-line hints
• click opens the reference popup
• popup can open full Find Usages
• dark theme rendering
• split editor behavior
• scrolling / viewport refresh behavior
• indexing refresh behavior

I also rebuilt the affected modules and the IDE image during development.

Follow-up scope intentionally excluded

• LSP / generic editor integration
• non-Java languages
• an alternative lazy, non-inline usage action mode

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