[Feature Request]: get rid of Gtk-WARNING/CRITICAL on Linux

### What would you like to happen?

It's hard to get rid of the GTK warnings in the Hop GUI scripts for Linux.
It's likely caused by issues in the SWT layer and doesn't affect the working of the GUI itself.

That's why I would propose to add the following expression after the startup line:

```
... 2>&1 | egrep -v "Gtk-WARNING|Gtk-CRITICAL|^$"
```

So this becomes:

```
"${_HOP_JAVA}" ${HOP_OPTIONS} -Djava.library.path="${LIBPATH}" -classpath "${CLASSPATH}" org.apache.hop.hop.Hop "$@" 2>&1 | egrep -v "Gtk-WARNING|Gtk-CRITICAL|^$"
```

### Issue Priority

Priority: 3

### Issue Component

Component: Hop Gui

Locate the Hop GUI Linux startup script and inspect the command that launches the Java application. Apply the requested filtering there, then verify that Gtk-WARNING and Gtk-CRITICAL lines are hidden while the GUI still starts and other output remains visible.

Written by the indexing model from the issue text.