Backport #11419, #11913, and #10638 to v7

[ptgott]

Edit two guides for Cloud users

Backports #11419

• Edit two guides for Cloud users

PAM guide

• Minor style/clarity/grammar edits
• Use a ScopedBlock to hide Cloud-irrelevant information in the MOTD
  section
• The organization of the original guide was a bit scrambled, so I
  attempted to reorganize it into a form that made more sense.

Tsh guide

• Use ScopedBlocks to provide scope-relevant information.

• Mention Machine ID in the "### SSH certificates for automation"
  section.

• Misc grammar/clarity/style edits

• Respond to PR feedback

Clarify two guides and two intro pages

Backports #11913

• Clarify two guides and two intro pages

See #11841

Make the Adding Nodes guide more usable for Cloud

• Add a ca_pin preset
• Clarify that tctl must be run on the local machine for Cloud users
• Structure the guide as a step-by-step tutorial. The guide already
  included sequences of sample commands, so all this took was to rename
  headings according to the "Step n/d." format and move the CA pinning
  section into the section on starting the Node.
• Add environment variables to use for storing a CA pin and invite
  token to sample commands, plus piped commands to extract these
  strings from the output of tctl commands.
• Use a ScopedBlock to hide the Node Tunneling section for Cloud users
• Indicate that the --auth-server flag in "teleport start" requires a
  port.

Add intros to the Admin and Operations menu pages

• Clarify the purpose of the Admin Guides and Operations sections
  by adding an intro paragraph to each page. Since these sections are
  similar in scope, I added links from one to the other with statements
  about how the two sections differ.

• Replace lists of links with Tiles.

GitHub SSO

• Move the step to create an OAuth app out of the Prerequisites and
  into its own step. This makes it easier to give the instructions
  to use a specific callback URL proper space.
• Be more explicit about the rp_ip value.
• Add explicit instructions for logging in to the cluster after
  creating the auth preference, including screenshots of expected
  results.

• Fix wording and linter issues following PR review

• Respond to PR feedback

Remove a misleading instruction re: CA pinning. Also move some text
about CA pinning to a more appropriate location.

Edit four Access Controls pages for Cloud users

Backports #11826

• Edit four Access Controls pages for Cloud users

See #10638

Access Controls Getting Started guide

• Add a tabbed Prerequisites section for users of different scopes
• Use a ScopedBlock to show OIDC and SAML instructions as Tabs for
  commercial Teleport users and GitHub instructions for OSS Teleport
  users
• Light style/grammar/clarity edits

Role Templates

• Tabbed Prerequisites section for different scopes
• Adjust the visibility of minor details using ScopedBlocks

Locking

• Add a scoped Tabs component to the Prerequisites section
• Add a ScopedBlock to hide CLI- and config file-specific instructions
  from Cloud users.

WebAuthn

• Add scoped Tabs to the Prerequisites section
• Move Tabs with TabItems for static configurations and dynamic
  resources into ScopedBlocks. This way, we don't have to show
  static configuration instructions to Cloud users.
• Remove duplicate config field explanations.
• Minor style/grammar edits

• Respond to PR feedback

• Change verbiage re: belonging to a role
• Remove U2F migration section