Adapt run_ds5_script.sh for recent Arm DS versions

Arm DS-5 has been superseded by Arm Development Studio. Do the necessary
changes to the EL3 payload scripts to migrate to the latter:

 - Rename run_ds5_script.sh into run_armds_script.sh.
 - The command-line debugger is now called armdbg.
 - The CDB entry string for Arm Juno development board has changed.

Change-Id: Idc640e7fcff790d5a1bf6e938e14a0dbc88029b9
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>