feat: As a user, I want to include the request body in the opa-input, so that I can reason about its contents

[wistefan]

Description

In order to make decisions based on the request body, the OPA-Plugin will also forward the body when configured to do so.

Fixes #11387

Checklist

• I have explained the need for this PR and the problem it solves
• I have explained the changes or the new features added to this PR
• I have added tests corresponding to this change
• I have updated the documentation to reflect this change
• I have verified that this change is backward compatible (If not, please discuss on the APISIX mailing list first)

[wistefan]

Is there anything I can do to get this PR forward?

[github-actions]

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[moonming]

@wistefan Please synchronize the master code to trigger all CI

[wistefan]

@wistefan Please synchronize the master code to trigger all CI

@moonming Thank you for the review, I updated.