fix(ecs): move service discovery configuration to react

[piradeepk]

Updated the service discovery section of the configure server group wizard to react. Created and updated a server group using both the existing UI and the updated UI and the generated json is the same.

       "serviceDiscoveryAssociations": [
        {
          "containerPort": 80,
          "registry": {
            "account": "ecs-my-aws-devel-acct",
            "arn": "arn:aws:servicediscovery:us-west-2:164281909131:service/srv-mmr3glofrvzvtpdv",
            "displayName": "spinnaker-ecs-ec2-demo-svc (srv-mmr3glofrvzvtpdv)",
            "id": "srv-mmr3glofrvzvtpdv",
            "name": "spinnaker-ecs-ec2-demo-svc",
            "region": "us-west-2"
          }
        }
      ],

Resolves: spinnaker/spinnaker#5482

[spinnakerbot]

The following commits need their title changed:

• 561a38b: Update

• 923e334: Update

• 42f0900: Test

• 1b30f15: Fix

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[piradeepk]

@allisaurus and @clareliguori please review

[allisaurus]

since this is firing when the registry drop-down is changed, when would we not find the registry? could newRegistry be search input (vs. an existing option)?

[piradeepk]

I was trying to maintain consistency with how the other properties are loaded in the configuration wizard currently (artifacts, container mappings, etc)