Remove dependent aliases and JSON CLI input support

[nehanene15]

Dependent aliases were originally built to remove columns that were not needed in row validations since unsupported data types (Structs, arrays) would throw errors. Now that we only bring down the columns we need ever since PR #599, we can get rid of dependent aliases.

We also supported JSON CLI inputs a while back (--tbls {source: table, target: table, ...}) that we don't support anymore. We can clean up this code (Example where we always try to decode JSON before parsing the arguments.