Add list.remove_duplicates() method

[AvitalOhayon]

Feature or enhancement

Proposal:

Rationale:

Currently there's no straightforward way to remove duplicates while preserving order. Common solutions like list(dict.fromkeys(lst)) or using sets are either non-intuitive or don't preserve order.

Proposed API:

lst = [1, 2, 2, 3, 1]
lst.remove_duplicates()  # returns [1, 2, 3]

Has this already been discussed elsewhere?
This is a minor feature, which does not need previous discusions elsewhere.

[graingert]

This is a pretty major feature, and would need to be discussed here first: https://discuss.python.org/c/ideas/6