[Feature Request]: UI freezes while typing in DB-metadata fields (e.g., Lookup table) in Apache Hop

### What would you like to happen?

Description
When editing transforms that rely on database metadata (e.g., Database Lookup), Hop’s UI becomes laggy/freezes while typing in fields like Lookup table (table name). It looks like metadata is being fetched/validated on every keystroke, blocking the UI thread.

The issue is more noticeable in larger pipelines (many hops/loops). It can also happen when opening/editing transforms such as Select Values, where the dialog seems to refresh metadata and the UI freezes.

Expected

Smooth typing without UI blocking.

Metadata loading/validation should be async and/or debounced.

Optionally, use a short-lived metadata cache per connection to reduce repeated calls.

### Issue Priority

Priority: 3

### Issue Component

Component: Hop Gui

Reproduce the freeze while typing in the Database Lookup table-name field and while opening or editing Select Values in a larger pipeline. Profile when database metadata is fetched or validated, then verify that typing remains responsive and that metadata work is asynchronous or debounced, with repeated calls reduced where appropriate.

Written by the indexing model from the issue text.