docs: add authz reference info in the circuit antehandler (backport #20146)

[mergify]

Description

Ref: #18632 (comment)

Teams are using the circuit ante as reference to copy into their networks. If their network uses authz, there is a security issue right away for them w/ nested authz Exec bypasses if you don't recursively check or block like dydx does.

Maybe the SDK should disallow nested authz Exec's anyways as a security precaution? Is there any actual reason to allow this. I can't think of a valid use case

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Summary by CodeRabbit

• Documentation
  • Enhanced comments for better understanding of nested authz.Exec messages handling in the AnteHandle method.

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This is an automatic backport of pull request #20146 done by [Mergify](https://mergify.com).