Qualification tool: Improve calculation of num of transitions for CPU fallbacks

[nartal1]

Describe the bug
This issue to track the task of improving number of transtions calculations when the tool detects CPU fallbacks for oprators not running on GPU.
Current implementation does a good job of calculating the number of transitions by flattening all the Execs per stage but there could be some scenarios where we might miss calculating the transitions correctly.
For example: Consider an Exec SMJ where SMJ Exec is fed from 2 Sort Execs. If an Exec similar to Sort is not supported on GPU, then the current implementation will calculate the number of transitions as 1 instead of 2. This could be improved.

PS: Current testing on subset of NDS queries and customer queries produced correct number of transitions.