Parse backtick-enclosed json

[peterychang]

Why are these changes needed?

Some models enclose json in markdown code blocks

Related issue number

resolves #6599. , #6547

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://github.com/microsoft/autogen/blob/main/CONTRIBUTING.md 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]

Codecov Report

Attention: Patch coverage is 82.14286% with 5 lines in your changes missing coverage. Please review.

Project coverage is 79.68%. Comparing base (d1d664b) to head (1f68afe).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
.../autogen_ext/models/anthropic/_anthropic_client.py	20.00%	4 Missing ⚠️
...p_chat/_magentic_one/_magentic_one_orchestrator.py	80.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6607   +/-   ##
=======================================
  Coverage   79.68%   79.68%           
=======================================
  Files         226      227    +1     
  Lines       16964    16989   +25     
=======================================
+ Hits        13517    13538   +21     
- Misses       3447     3451    +4     

Flag	Coverage Δ
unittests	79.68% <82.14%> (+<0.01%)	⬆️

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[victordibia]

LGTM.
FYI, I have merged in #6540 which checks if model supports structured json and uses that.
Your impl seems to work well on top of that (you try to parse json from whatever comes from the model). A final doublecheck would be good.

I am approving this for now.
In general, it might be a good idea for us to just encourage devs to only use models with structured output (for better reliability ) with m1.

[afourney]

Looks good. I appreciate the changes.