WIP: avonbertoldi/feature/multi subnet

• feat: support multiple subnets and security groups

• test: security-group limits

• test: check for when cluster or region missing

• refactor: code review changes

• chore: resolve config review feedback
  Signed-off-by: Marais Van Zyl marais.vanzyl@verizonconnect.com

• chore: review feedback
  Signed-off-by: Marais Van Zyl marais.vanzyl@verizonconnect.com

• docs: update readme descriptions
  Signed-off-by: Marais Van Zyl marais.vanzyl@verizonconnect.com

• refactor: validate config after load

• test: add unit tests for config validation
  Signed-off-by: Marais Van Zyl marais.vanzyl@verizonconnect.com