Implement a public setter for client accountID

[mergenci]

• Required in order to address changes introduced by: Replace AWS Region metadata from names with endpoints hashicorp/terraform-provider-aws#40335

• Specifically this commit in the PR linked above: hashicorp/terraform-provider-aws@fa813c5

• Given that accountID getter accepts a context parameter, which is currently unused, we may have to implement more substantial changes in future.

• I tested the implementation by consuming it in Bump Terraform provider version to v5.82.2 crossplane-contrib/provider-upjet-aws#1629. I was able to provision a DynamoDB table and delete it.

[github-actions]

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[turkenf]

Thank you @mergenci, LGTM 🙌