If the Threading::BackgroundAction for filesystem indexing in
FileProvider hadn't finished by the time the main thread exited, it
would still try to access the FileProvider object that lived in the main
thread, thereby causing a segfault and crashing. This commit prevents
FileProvider from being destroyed while the background thread is still
running by giving the background thread a strong reference to its
FileProvider.
Instead of making it a void function, checking for an exception, and
then receiving the relevant result via VM::last_value(), we can
consolidate all of this by using completions.
This allows us to remove more uses of VM::exception(), and all uses of
VM::last_value().
Using fstatat() allows the kernel to do relative path resolution as
opposed to absolute path resolution, which is significantly faster
and allows us to build the path cache sooner. :^)
Result classes now return their bitmap via a virtual Gfx::Bitmap*
getter. This effectively makes bitmap fetching lazier, since only
results that end up on screen actually get asked for their bitmap.
This drastically reduces the amount of work done by the FileProvider
background worker.
When searching in Assistant, we now dispatch some background jobs to
query the whole filesystem. Activating a result will use the Desktop
launcher's default way of opening that file or directory.
When launching Terminal via Taskbar we change to the users home
directory. For consistency, let's also `chdir` to `/home/anon` when
launching apps via Assistant's AppProvider.
