Update tutorial examples, reference to register_reply.

[ekzhu]

Why are these changes needed?

1. Fixes some examples and text incompatibilities.
2. Add references to registered_reply method.
3. Add illustration for human-in-the-loop component.

Related issue number

#1932

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://microsoft.github.io/autogen/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 37.30%. Comparing base (c75655a) to head (1f5ce5d).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1941   +/-   ##
=======================================
  Coverage   37.30%   37.30%           
=======================================
  Files          64       64           
  Lines        6910     6910           
  Branches     1519     1519           
=======================================
  Hits         2578     2578           
  Misses       4109     4109           
  Partials      223      223           

Flag	Coverage Δ
unittests	37.30% <ø> (ø)

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