LIVE-5319 Bump simple-configuration to 1.5.7

[waisingyiu]

What does this change?

This PR bumps the simple-configuration library to a newer version 1.5.7 from version 1.5.6

There are API breaking changes in simple-configuration between version 1.5.6 and version 1.5.7. Please refer to guardian/mobile-apps-api#2797 for details.

This PR makes the following code changes for this new version of simple-configuration:

1. In order to detect whether the service is running locally, I added a check on the environment variable "MOBILE_LOCAL_DEV" - if this environment variable is present, it assumes DevIdentity and bypassed the AppIdentity.whoAmI call (bypassing AppIdentity.whoAmI in local deployment was recommended in Discourage usage that causes long startup delays simple-configuration#28). Otherwise it invoked AppIdentity.whoAmI and it is still able to return a DevIdentity if whoAmI fails to load the identity from EC2 tags / lambda environment variables.
2. Pass in the region to SSMConfigurationLocation constructor
   using the region from AwsIdentity
3. The simple-configuration library has to be bumped in mobile-logstash-encoder as well (LIVE-5891 Bump simple configuration to 1.5.7 mobile-logstash-encoder#17). Otherwise, the microservice fails to start up because the mobile-logstash-encoder throws fatal exception due to the breaking API change.

How to test

It was deployed to CODE, and we validated the service by registering a token and sending a notification to debug build.

Logs were written properly:

[silvacb]

👍