feat: use original Expect scripts for UART validation

To avoid having to implement custom Python post-expect scripts for every
payload that might use a non-primary UART, and to make use of as much
prior art as possible, this change replaces the OpenCI-only post-expect
scripts with the same one uses used by both the local and on-premises CI.

The original Expect scripts have been amended to identify whether they're
being run in the postprocessing step and, if so, load the UART log from a
file rather than connecting to the FVP over Telnet.

Change-Id: I61a5859de4f3f62b50deaffe84580206ec411c99
Signed-off-by: Chris Kay <chris.kay@arm.com>
11 files changed