feat(agentcore): add identity credential providers L2 constructs

[krokoko]

Issue # (if applicable)

Add L2 CDK constructs for:

• https://docs.aws.amazon.com/AWSCloudFormation/latest/TemplateReference/aws-resource-bedrockagentcore-oauth2credentialprovider.html
• https://docs.aws.amazon.com/AWSCloudFormation/latest/TemplateReference/aws-resource-bedrockagentcore-apikeycredentialprovider.html

to the agentcore package. Update also the gateway construct to support these new ones when configuring outbound auth for a target

Reason for this change

Feature gap

Description of changes

• Updated the existing gateway construct
• Added a new folder with the

Describe any new or updated permissions being added

Exposed the permissions specific to the identity providers

Description of how you validated changes

• added unit tests
• added integration tests

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

[github-actions]

⚠️ Experimental Feature: This security report is currently in experimental phase. Results may include false positives and the rules are being actively refined.
This security report is NOT a review blocker. Please try merge from main to avoid findings unrelated to the PR.
To suppress a specific rule, see Suppressing Rules.

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	Tests	Passed ✅	Skipped	Failed
Security Guardian Results	96 ran	96 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.
This security report is NOT a review blocker. Please try merge from main to avoid findings unrelated to the PR.
To suppress a specific rule, see Suppressing Rules.

---

	Tests	Passed ✅	Skipped	Failed
Security Guardian Results with resolved templates	96 ran	96 passed

Test	Result
No test annotations available

• View Security Guardian Results with resolved templates