Inconsistencies in PEP 1 regarding number assignment

#3163 updated PEP 1 so the PEP number should be worked out by the author on PR creation, not assigned by an editor once approved.

There are a few places that mention "assign"ing a number and seem a bit inconsistent with this.

1. In https://peps.python.org/pep-0001/#pep-editors

   The PEP editors are individuals responsible for managing the administrative and editorial aspects of the PEP workflow (e.g. assigning PEP numbers, ...

   A minor one, I can see an argument for leaving it as I guess PEP editors do still "manage" the numbers, but maybe there's a clearer wording.

2. In https://peps.python.org/pep-0001/#submitting-a-pep

   • Once approved, they will assign your PEP a number.

   Confusing, as the first task in the list is to select a PEP number yourself.

   Developers with write access to the PEP repository may claim PEP numbers directly by creating and committing a new PEP.

   This no longer seems relevant, anyone can claim a pep number.

   Getting a PEP number assigned early can be useful for ease of reference, especially when multiple draft PEPs are being considered at the same time.

   Same with this.

3. In https://peps.python.org/pep-0001/#discussing-a-pep

   As soon as a PEP number has been assigned and the draft PEP is committed to the PEP repository, a discussion thread for the PEP should be created

   Not really incorrect, but mentioning it seems a bit meaningless now.

   Once the PEP is assigned a number and committed to the PEP repository, substantive issues should generally be discussed on the canonical public thread

   Same here, should just mention "committed to PEP repository".

4. In https://peps.python.org/pep-0001/#pep-header-preamble

   The Created header records the date that the PEP was assigned a number

   The wording here isn't incorrect, but the change to how numbers are assigned seems to imply that now the "created" date can differ quite significantly from when it is published to https://peps.python.org. It is not clear that this was effect was considered, so I'll create a separate issue to discuss it.

Read PEP 1 at peps.python.org/pep-0001, focusing on the PEP editors, Submitting a PEP, Discussing a PEP, and PEP header preamble sections identified in the issue. Compare each reference with the current number-claiming workflow, then update wording consistently and verify the rendered PEP 1 no longer describes obsolete assignment steps.