lib: flatten all loose components into one lib

lib/ was starting to get messy and inconsitent. Files being either
dumped in the root or in sub-directories without a clear plan.
Move all library components into one single folder and call it 'os'.

Signed-off-by: Anas Nashif <anas.nashif@intel.com>

lib/os/CMakeLists.txt

@@ -0,0 +1,17 @@
+zephyr_sources_if_kconfig(base64.c)
+
+zephyr_sources(
+  crc32_sw.c
+  crc16_sw.c
+  crc8_sw.c
+  crc7_sw.c
+  fdtable.c
+  mempool.c
+  rb.c
+  thread_entry.c
+  work_q.c
+  )
+
+zephyr_sources_ifdef(CONFIG_JSON_LIBRARY json.c)
+
+zephyr_sources_if_kconfig(ring_buffer.c)