Revert (sonic-net#2599)

b34a540 [generate_dump] Fix for deletion flow for all secret files from show-techsupport dump (sonic-net#2571)
258ffa0 [generate_dump] Optimize the execution time of 'show techsupport' CLI by parallel function execution (sonic-net#2512)
572c8cf Optimize the execution time of the 'show techsupport' script to 5-10%, (sonic-net#2504)

This reverts commits
b34a540
258ffa0
572c8cf