RESUMABLE: proposed rename section headers discussing state concepts

[LPardue]

@gstrauss provided the following feedback on https://lists.w3.org/Archives/Public/ietf-http-wg/2025JulSep/0094.html wrt Section 4.1

These headings are misnamed

• 4.1.1 Offset -> Upload-Offset
• 4.1.2 Completeness -> Upload-Complete
• 4.1.3 Length -> Upload-Length
• 4.1.4 Limits -> Upload-Limit

Considering the doc states that the server is required to keep state, such as the target resource, it appears that important state items are not all clearly defined under the topic "State".

Section 4.1 defines properties of the state of an upload. It also defines headers to transfer state information between endpoints. Therefore this is a subjective editorial issue.

[LPardue]

I made one, rather large, proposal for this on #3199 but happy to entertain other options to weigh up the right choice