Reliability UI track: Reducing to have 5 discrete values

[Sande3p]

Gone those days when UI contest were easy & small.
Now an average UI contest is 3x more bigger & complex than the UI contests of 2011-12.

A better solution could be reducing reliability benchmark to 5 contest for UI track.

[hokienick]

@adroc-tc already working on making prototype challenges smaller. Taking a different approach.