Rename top-level kas/ to ci/

The files in kas/ are not generic Kas files, but instead designed
specifically and solely around the CI system.

Change-Id: I30082392ad2231a4c1c41e54a292595adf81715b
Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>

ci/bootstrap.yml

@@ -0,0 +1,9 @@
+header:
+  version: 9
+
+target:
+  - binutils-cross-aarch64
+  - gcc-cross-aarch64
+  - python3-native
+  - opkg-native
+  - rpm-native