[web] No vertical scroll in the report details view tree structure

[whisperity]

Describe the bug
If the screen is too small in terms of width, the tree view when viewing a Report becomes useless because there is no way to vertically scroll to read the individual elements.

CodeChecker version
6.23 (.0, I think, but the header only says 6.23)

To Reproduce

1. Open a bug report.
2. Constrict the window to be half of the screen, either by using a tiling window manager (such as i3), a tiling plugin for a compositor (such as Krohnkite) or by manually executing a tiling using Meta-←/→.

For example, the bug notes are not visible here, only their sequence:

Expected behaviour
A scroll bar appears at the bottom so I can scroll vertically.
A multi-directional scroll appears when pressing Mouse3, so I can drag scroll vertically.

Desktop

• OS: Ubuntu 22.04
• Browser: Firefox
• Version: 122.0
• Screen resolution: 1920×1080

Additional context
Vertical scrolling and drag scrolling are properly supported as-is in the code viewer.

There is a little knob which can be dragged to change the layout and increase the total width of the tree structure. However, this decreases the total width of the code viewer. Moreover, 90+% of the tree view is completely uninteresting if someone wants to jump between the notes belonging to a single bug report, so I don't want to increase the total width just to be able to read something that is in the "middle" centre of the tree view...