BREAKING CHANGE: gtk-layer-shell is now required and unconditionally
used. The corresponding config option is removed.
As a part of preparation for future versions of GTK, remove an ability
to use wlr-layer-shell directly. The APIs it required were dropped in
GTK4, and with the menus/tooltips positioning issue being practically
unsolvable it doesn't make sense to keep maintaining the code.
We already use it without checking (`<gio/gdesktopappinfo.h>` in
wlr/taskbar), it's a transitive dependency of GTK and it's always
available on Unix platforms.
The `<experimental/filesystem>` and `-lc++experimental` aren't needed
since LLVM 9.0. And since we now require C++20, checking for the
`<filesystem>` support shouldn't be necessary either.
Previously, the only way to select all the module labels was with the
following kind of selector:
```css
.modules-left > widget > label,
.modules-center > widget > label,
.modules-right > widget > label {
/* ... */
}
```
(and a matching block for the `box` containers).
Now, this can be expressed as
```css
label.module, box.module {
/* ... */
}
```
Background and Motivation
-------------------------
When the `hwmon-path-abs` and the `input-filename` fields are used for
the temperature module, we evaluated the following path:
```
[hwmon-path-abs] / [gap] / [input-filename]
```
where `gap` is the first file or directory in the `hwmon-path-abs`
directory. This usually works but it doesn't seem to work for NVME or
WiFi temperature sensors. For those cases, there are a bunch of other
files in the `hwmon-path-abs` directory. In the bad case, the first
selected file is not the one with the prefix `hwmon` and we end up
checking the wrong location for the `input-filename`.
Change description
------------------
We are simply going through the `hwmon-path-abs` directory and searching
for the first file/directory that begins with `hwmon`.
Test case
---------
I tested this on a AMD based Framework 13 laptop.
