Feature: Add option to show files from all subfolders recursively (flat view feature)

### What feature or improvement do you think would benefit Files?

sometimes i have 100 folders, but only 500 files. in this case i fire up XnViewMP to browse the parent folder recursively. this way i can finnish my work in a fraction of the clicks, and im less likely to forget doing something.

### Requirements

add to folder right click context menu "Show all files (including subfolders)"

### Files Version

3.0.15.0

### Windows Version

10.0.22631.2861

### Comments

_No response_