Change key/secret to optional in apoc.nlp calls for AWS

[bbenzikry]

Currently verifyKey is called for key & secret when using apoc.nlp.aws procedures.
This poses several issues, especially under an orchestrated environment ( we use k8s )

1. We don't want to rely on key/secret use ( we prefer using roles when calling the AWS APIs. specifically via IRSA )

2. As we have to explicitly use credentials, we rotate them. in our setup Vault is in charge of rotating keys and the key / secret pair is passed to the apoc static value storage via environment variables.
   This has the downside of the need to allocate a new pod, which means we can encounter call failures until the original pod is replaced.

Note: We considered mounting a secret volume, but that also has the same downside as currently kubernetes secret updates don't work for subPath mounts ( which is required if we mount into the conf/ dir without overriding neo4j.conf, as it's populated in the official docker image entrypoint )
This could potentially be circumvented if we can change the apoc.conf location via another variable ( I would love to hear whether this is possible )

Expected Behavior (Mandatory)

When called without key and secret, AWS calls should fall back to normal credential chain ( env var, instance profile, role etc. )

Actual Behavior (Mandatory)

Failed to invoke procedure `apoc.nlp.aws.entities.graph`: Caused by: java.lang.IllegalArgumentException: Missing parameter `key`. An API key for the Amazon Comprehend API can be generated from https://docs.aws.amazon.com/sdk-for-java/v1/developer-guide/setup-credentials.html

Specifications (Mandatory)

Versions

• OS: EKS, several underlying OS ( all linux ), official docker build for 4.1
• Neo4j: 4.1
• Neo4j-Apoc: 4.1.0.0