File-open dialog: support manually entered wildcard patterns

[qgppl]

Description of the Issue

File-Open dialog ignores manually entered wildcard patterns

Steps to Reproduce the Issue

1. File - Open
2. In Filename: enter a wildcard pattern e.g.: "*abc*.txt"
3. Press Enter

Expected Behavior

Dialog stays open, displaying only files which match the entered pattern for further browsing

Actual Behavior

Dialog closes and all files matching the wildcard filespec are opened as tabs

[sasumner]

The "Expected Behavior" as per the above is what happens in 7.5.9 when one has Settings (menu) -> Preferences... -> Default Directory -> Use new style dialog... TICKED.

When this checkbox is UNTICKED, then the "Actual Behavior" above is what occurs (although I'd add to the description so that it reads "Dialog closes and all files matching the wildcard filespec are opened as tabs").

[qgppl]

This seems to have been introduced alongside support for forward slash in paths (556901b). Should the current behavior should be treated as a feature then?