UX design: Request an extension feature

Update: Keeping issue in backlog for consideration later. At this time if a service partner needs to delay releasing a language, they create a new release plan and request an APEX extension via S360/CLC.

Use Case: As an Azure service engineer, I want to request an extension for one or more SDK languages so that I can release only the languages that are ready by the specified date. Part of https://github.com/Azure/azure-sdk-tools/issues/6597.

**Success criteria**
- Design pattern is scalable and can be applied across other apps to create a coherent experience for service partners.
- Design pattern is pressure-tested for accessibility, color, and usability.
- Design pattern reuses common Fluent components.

**Tasks**

- [x] Create lo-fi designs for review
- [ ] Refine design
- [ ] Hand-off for implementation