refactor: ai-content-moderation to ai-aws-content-moderation

[shreemaan-abhishek]

Description

The current plug-in configuration abstraction turned out to be a bad design choice as the moderation mechanism is hard-coded to plugin logic, if we use other AI content moderation services, there will be huge differences in how the content moderation is done.

So, this PR refactors ai-content-moderation plugin by making it specific for ai-aws-content-moderation.

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)

[membphis]

CI failed, pls fix those first

[shreemaan-abhishek]

CI failed, pls fix those first

seems like flaky error, I have re-run the CI.

[membphis]

need to update the doc too:

[membphis]

ci failed