`view.prep_slice()`: support quoted lists of characters as inputs

[yunjunz]

Description of proposed changes

• view.prep_slice(): support quoted lists of characters as inputs so that its parsing behavior is the same as the one in command line

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.
• [x] If modifying functionality, describe changes to function behavior and arguments in a comment below the function declaration.
• [x] If adding new functionality, add a detailed description to the documentation and/or an example.