[Task]: Replace RemoteSettings with kinto.python client

[KevinMind]

Description

There is a single missing feature in the officially supported kinto python client preventing us from using it. Kinto/kinto-http.py#103

We need to add support for adding attachements to records. Should be a fairly trivial patch as there is already an example implementation in the issue.

After we finish soft blocking we could consider landing this patch and switching to the client so we can remove the RemoteSettings class from our code base.

Acceptance Criteria

Milestones/checkpoints

Beta Give feedback

1. A sentence describing the first milestone/checkpoint

Checks

• If I have identified that the work is specific to a repository, I have removed "repository:addons-server" or "repository:addons-frontend"

┆Issue is synchronized with this Jira Task