Update add_filter with checks and append suffix Decision if necessary

Driven by the comment from @pkoppenb here this MR introduces checks to add_filter and adds suffix Decision if not present in the line name.

This would avoid mistakes by users who have to type Decision explicitly. So the code would change from:

filter = add_filter("filter_name",f"HLT_PASS('{line_name}Decision', '{line_name2}Decision')")

to

filter = add_filter("filter_name",f"HLT_PASS('{line_name}', '{line_name2}')")

To be tested with: Analysis!892 (merged)