Kernel+Userland: Remove loadable kernel moduless

These interfaces are broken for about 9 months, maybe longer than that.
At this point, this is just a dead code nobody tests or tries to use, so
let's remove it instead of keeping a stale code just for the sake of
keeping it and hoping someone will fix it.

To better justify this, I read that OpenBSD removed loadable kernel
modules in 5.7 release (2014), mainly for the same reason we do -
nobody used it so they had no good reason to maintain it.
Still, OpenBSD had LKMs being effectively working, which is not the
current state in our project for a long time.
An arguably better approach to minimize the Kernel image size is to
allow dropping drivers and features while compiling a new image.

Kernel/CMakeLists.txt

@@ -219,7 +219,6 @@ set(KERNEL_SOURCES
     Syscalls/mkdir.cpp
     Syscalls/mknod.cpp
     Syscalls/mmap.cpp
-    Syscalls/module.cpp
     Syscalls/mount.cpp
     Syscalls/open.cpp
     Syscalls/perf_event.cpp
@@ -528,4 +527,3 @@ serenity_install_headers(Kernel)
 serenity_install_sources(Kernel)
 
 add_subdirectory(Prekernel)
-add_subdirectory(Modules)