json: Speed up `json.dump()` with non-default options.

[methane]

Feature or enhancement

Proposal:

By making json.dump() skip creating a JSONEncoder instance and calling its encode() method, and instead invoke the internal encoding logic directly, we can reduce the time required to encode small JSON objects by about 20% with the default options and about 50% with non-default options.

Has this already been discussed elsewhere?

I have already discussed this feature proposal on Discourse

Links to previous discussion of this feature:

faster-cpython/ideas#742

Linked PRs

• gh-158270: json: make dumps() skip JSONEncoder #158271