Delete out-of-tree antlion code.

This change removes all files from antlion except the README.md
that now points to antlion in-tree.

Fixed: 440387588
Change-Id: I86f5e08902787439cc48ec965b807e5d77dbb8d8
Reviewed-on: https://fuchsia-review.googlesource.com/c/antlion/+/1353925
Reviewed-by: Adam Schrems <schrems@google.com>
Reviewed-by: Ritu Gupta <guptaritu@google.com>
Reviewed-by: Pavan Kumar Juturu <jpavankumar@google.com>
Commit-Queue: Charles Celerier <chcl@google.com>
Fuchsia-Auto-Submit: Charles Celerier <chcl@google.com>