Closes #33417

Focus the guide more on its stated topic by moving tangentially related
reference information at the end of the guide to more appropriate pages.

- Replace the `search_as_roles` section with a link. Much of the "Next
  steps" section is a long list of examples of Teleport roles that an
  admin could assign to `search_as_roles`. This is unnecessary, since a
  user familiar with a Teleport role won't need this information to
  understand `search_as_roles`. It is not the job of the Resource Requests
  guide to teach users about Teleport roles.
- Condense the "Next steps" guidance. There are "Next steps" sections.
  Make them one. Also turn the section re: Access Request plugins into a
  bullet.
- Move instructions for searching for and requesting Kubernetes
  resources into the tsh guide. These instructions are end users, so
  move them to the appropriate guide to make them more discoverable.

Closes #33417

Focus the guide more on its stated topic by moving tangentially related
reference information at the end of the guide to more appropriate pages.

- Replace the `search_as_roles` section with a link. Much of the "Next
  steps" section is a long list of examples of Teleport roles that an
  admin could assign to `search_as_roles`. This is unnecessary, since a
  user familiar with a Teleport role won't need this information to
  understand `search_as_roles`. It is not the job of the Resource Requests
  guide to teach users about Teleport roles.
- Condense the "Next steps" guidance. There are "Next steps" sections.
  Make them one. Also turn the section re: Access Request plugins into a
  bullet.
- Move instructions for searching for and requesting Kubernetes
  resources into the tsh guide. These instructions are end users, so
  move them to the appropriate guide to make them more discoverable.