executors: improve admin page

[LawnGnome]

Plan of attack

• [x] Remove RxJS and convert entirely to Apollo.
• [x] Add polling.
• [x] Add storybook.
• [ ] Improve empty state.
• [ ] Show and link to current jobs per executor.
• [ ] Expose more info:
  • [ ] Number of CPUs.
  • [ ] Memory.
  • [ ] CPU usage (graph?).
  • [ ] Memory usage (graph?).
• [ ] Ask design for input.

Eventually closes #27546.

Test plan

TBC; presumably some combination of storybook coverage and live testing.

App preview:

• Web

Check out the client app preview documentation to learn more.