inspect: Split code into separate files.

inspect: Split code into separate files.

The src/inspect.c file had grown rather large -- 3,500 lines.  Split
it across several files according to function.

This is just moving code.

After the split the files are more evenly divided:

  536 src/inspect_apps.c
  766 src/inspect.c
  537 src/inspect_fs.c
  404 src/inspect_fs_cd.c
  785 src/inspect_fs_unix.c
  535 src/inspect_fs_windows.c
 3563 total
(cherry picked from commit 3336b5448f12c9eb25bf7a0cecda1315c4cf07ea)