Replace aliases to builtins with imports

[hamdanal]

• Closes #xxxx (Replace xxxx with the Github issue number)
• Tests added: Please use assert_type() to assert the type of any return value

These aliases are not needed as they are there to avoid name collisions with methods defined in the class. Name collisions can be avoided by importing these symbols from builtins under a different name. This has no functional change to type checkers but has two tiny advantages:

1. IDEs now display the type as builtin type instead of an alias that doesn't exist at runtime
2. Linters like ruff can now understand that the symbol used is exactly the builtin one and can detect more bad usages (see the comment below)

[hamdanal]

ruff can now detect that _str shadows the literals we accept so it started complaining here

[Dr-Irv]

and this is a better change because the set of strings that are accepted is limited

[Dr-Irv]

thanks @hamdanal

[Dr-Irv]

and this is a better change because the set of strings that are accepted is limited