chore: make in-house openapi generators more reusable

[hamidzr]

Ticket

Description

Remove the dependency on determined package and BaseSession

https://hpe-aiatscale.slack.com/archives/C6D7MDSQ5/p1722972189991699

Test Plan

• check the diff in the generated code it should just show a set of

  -    session: "api.BaseSession",
  +    session: "RequestHandler",

Checklist

• [ ] Changes have been manually QA'd
• [ ] New features have been approved by the corresponding PM
• [ ] User-facing API changes have the "User-facing API Change" label
• [ ] Release notes have been added as a separate file under docs/release-notes/ See Release Note for details.
• [ ] Licenses have been included for new code which was copied and/or modified from any external code