feat(bedrock-agentcore-alpha): support No Authorization for AgentCore Gateway

[mazyu36]

Issue # (if applicable)

N/A

Reason for this change

Add support for No Authorization (authorizerType=NONE) for AgentCore Gateway. This enables use cases such as:

• Building public MCP servers
• Skipping gateway-level authentication while enforcing tool execution-level authentication using Gateway Interceptors (Ref)

Description of changes

Added NONE to GatewayAuthorizerType enum.

Describe any new or updated permissions being added

N/A

Description of how you validated changes

Add a unit test and an integ test.

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[aws-cdk-automation]

(This review is outdated)

✅ Updated pull request passes all PRLinter validations. Dismissing previous PRLinter review.

[github-actions]

⚠️ Experimental Feature: This security report is currently in experimental phase. Results may include false positives and the rules are being actively refined.
Please try merge from main to avoid findings unrelated to the PR.

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	Tests	Passed ✅	Skipped	Failed
Security Guardian Results	48 ran	48 passed

Test	Result
No test annotations available

• View Security Guardian Results

[github-actions]

⚠️ Experimental Feature: This security report is currently in experimental phase. Results may include false positives and the rules are being actively refined.
Please try merge from main to avoid findings unrelated to the PR.

---

	Tests	Passed ✅	Skipped	Failed
Security Guardian Results with resolved templates	48 ran	48 passed

Test	Result
No test annotations available

• View Security Guardian Results with resolved templates