Add support for Consul 1.15.x

[cthain]

Changes proposed in this PR:

This PR adds support for:

• Acceptance testing with the latest N-2 Consul versions (Currently, 1.15.0, 1.14.4, and 1.13.6)
• Using the Consul HTTP API to read the client ACL token after performing the consul login using the AWS auth method. There is an issue with using the consul acl token read -self on Consul 1.15.0, so mesh-task and gateway-task have been updated to use the HTTP API instead.
• Bumps the Envoy version to v1.23.1 and switches to distroless
• Uses the new consul-ecs net-dial command for ECS health checks on the sidecar-proxy container.

How I've tested this PR:

• Acceptance tests

How I expect reviewers to test this PR:

:eyes:

Checklist:

• [x] Tests added - Added Consul 1.15.0 to acceptance test matrix.
• [x] CHANGELOG entry added

[cthain]

I'm curious... what templating system are those .tpl files using?

The templates are rendered in the module using the Terraform templatefile function