This makes code easier to read and more consistent between C++ and Java.
Also update clang-format settings to always add a line break (even if no braces are used).
Previously this would list ALL /dev/video* devices. In recent versions of
Linux this leads to listing duplicate devices, as many USB cameras provide
both a video device and a metadata device, and only the video device can
actually be used for streaming.
std::scoped_lock was introduced in C++17 and is strictly better than
std::lock_guard as it supports locking any number of mutexes safely.
It's also easier to use than std::lock for locking multiple mutexes at
once.
This is primarily for use on Linux to get by-id or by-path device names.
This information is now part of UsbCameraInfo.
A new entry point was added to UsbCamera to get that camera's UsbCameraInfo.
The alternate paths are also returned in EnumerateUsbCameras.
This avoids a number of shutdown use-after-free races by controlling the
destruction order. It also is a prerequisite to making the internal
interfaces mockable for unit testing.
