Enable IPv6 support for SSM Client

[TheanLim]

Summary

Enable SSM client to automatically use dualstack endpoints when running on IPv6-only instances.

Ref PR: #4580

Implementation details

1. Client Configuration Updates
   i. Modified NewSSMClient to accept IPCompatibility parameter
   ii. Set useDualStackEndpoint based on IPv6 compatibility status
2. Task Resources
   1. SSM client is mainly used by TaskResources such as FSxWindowsFileServer, SSMSecret, and CredentialSpecs.
   2. Added an ipCompatibility field to each task resource.
      1. Updated New* constructors to accept an additional ipCompatibility parameter. New* is invoked when there's a new incoming task that requires task resources.
      2. Initialize() is invoked when Agent restarts and reinitialize task resources. Updated such that the ipCompatibility field is populated.
      3. Config.InstanceIPCompatibility is the source of value. Updated call chains so that the ipCompatibility is passed down correctly

Testing

Setups done:

• Set IPCompatibility to NewIPv6OnlyCompatibility
• Pin the functional test suite to run on a dualstack subnet (agent is currently connecting to control plane via IPv4).
• Update the SSM Client to use the SSM Pre-prod endpoint for testing purpose, as the dualstack endpoint is still a work in progress. Once the dual-stack endpoint functionality is production-ready, no additional changes will be required on top of this PR.
  • Create SSM Parameters needed by the functional test suite on the Pre-prod

Executed functional test suite on dualstack subnet. Verified all tests passed and pre-prod endpoint usage through docker container logs.

level=debug time=2025-05-15T17:43:10Z msg="Test: Configuring SSM custom endpoint"

New tests cover the changes: no

Description for the changelog

Enhancement: SSM Client resolves to dualstack endpoint on IPV6-only instances

Additional Information

Does this PR include breaking model changes? If so, Have you added transformation functions?

Does this PR include the addition of new environment variables in the README?

Licensing

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

[danehlim]

nit (non-blocking): Could do a more specific check using assert.Equal here, given that config (or testConfig in this case) contains what we expect to be the source of truth for IP compatibility.

[TheanLim]

Agreed. Ignoring this for now as we implicitly check it in the ssmClientCreator.NewSSMClient input args

fv, _, ssmClientCreator, _, _, mockSSMClient, _, _ := setup(t)
...
ssmClientCreator.EXPECT().NewSSMClient(gomock.Any(), gomock.Any(), testConfig.InstanceIPCompatibility).Return(mockSSMClient, nil),

Thanks