cam-tool/analyze: Introduce event alarm margin cmd line parameter

This patch introduces a command line argument "margin" to the cam-tool
analyze option to add a user-specified margin which will be added to the
"timeout" parameter calculated as a result of running the
cam-app-example in calibration mode. This allows users to fine-tune the
event alarm timeout based on deployment use cases.

Signed-off-by: Rahul Singh <rahul.singh@arm.com>