Add buildOptions to ECR config

[martinezpl]

Adds a buildOptions parameter to ECR config block in order to enable passing arbitrary flags to the docker build command, which builds the image that is sent to ECR.

e.g.

provider:
  ecr:
    scanOnPush: true
    images:
      image:
        path: ./image/
        file: Dockerfile.dev
        buildArgs:
          STAGE: ${sls:stage}
        buildOptions:
          [
            '--tag',
            'v1.0.0',
            '--add-host',
            'example.com:0.0.0.0',
            '--ssh',
            'default=/path/to/private/key/id_rsa',
          ]

Closes: #11255, #10712