feat!: Upgrade min AWS provider and Terraform versions to 6.0 and 1.5.7 respectively

[bryantbiggs]

Description

Motivation and Context

• Resolves Set http_put_response_hop_limit = 1 by default #3333
• Resolves AWS Provider 6.0.0 breaks self-managed-node-group #3383
• Closes feat: Remove elastic_gpu_specifications and elastic_inference_accelerator #3385
• Resolves Support AWS provider v6 #3386
• Resolves Error: Unsupported block type in v20.14.0 #3388
• Resolves v21 Proposed Changes #3394
• Resolves Self-managed-node-group Unsupported block type #3407

Breaking Changes

How Has This Been Tested?

• I have updated at least one of the examples/* to demonstrate and validate my change(s)
• I have tested and validated these changes using one or more of the provided examples/* projects
• I have executed pre-commit run -a on my pull request

[bryantbiggs]

finding the variable optional attributes to be a bit challenging:

• fix: Remove coalesce() to ensure value precedence is honored terraform-aws-ecs#307
• fix: Remove non-functional container_definition_defaults terraform-aws-ecs#312

which is why this hasn't proceeded. once those are stabilized a bit, we can apply those learnings here and proceed

[roncohen4]

@bryantbiggs Looking forward for this release, it's blocking me from upgrading AWS provider to 6.x
Any estimation for this to be done any time soon?