doc string description for `defaults/objects/simulation/utils` sub-modules

[yunjunz]

Description of proposed changes

For all scripts within defaults/objects/simulation/utils sub-modules:

• add a doc string at the top to describe its purpose

• remove #! at the top from the remaining scripts (most scripts are already like that), since they are not needed.

Reminders

• [x] Pass Pre-commit check (green)
• [x] Pass Codacy code review (green)
• [x] Pass Circle CI test (green)
• [x] Make sure that your code follows our style. Use the other functions/files as a basis.