ci: Update to the ACS 2.1 test image

Use the released version of the ACS test result parser.
Use the latest 2.1 release of the ACS test image.
The 2.1 test image now collects the test results in the same directory so we no longer have to move some of them around.
BSA result file is now utf16-le encoded so we now read it in as a utf16-le file.
Ensure the results do not get mixed with other project results by putting them in a project specific area in artifactory. This ensures the clean up task does not effect other projects test files.
Validate we have got the correct test results but checking the launch project and job ids match whats expected.
Increase the number of retained builds.
Detect BSA result file encoding.
The systemd-conf base recipe already contained a file called system.conf so by adding the same file in the append recipe we were overwriting the original and installing 2 copies of the same file into the image. The file in the append recipe has now been renamed to avoid this.

Signed-off-by: Drew Reed Drew.Reed@arm.com