Realign naming of configuration settings

Configuration setting name should only use caps to align to how environment variables are set. On Linux environment variables are case-sensitive. As a result, environment variables are commonly expressed with all caps.

To reduce confusion when setting configuration via environment variables all configuration names should be updated to use only caps. This will be a breaking change and will affect the following configuration options:

- `Azure_AKSMinimumVersion`
- `Azure_AKSNodeMinimumMaxPods`
- `Azure_AllowedRegions`
- `Azure_MinimumCertificateLifetime`

Renamed configuration options will be:

- [x] `AZURE_AKS_CLUSTER_MINIMUM_VERSION` instead of `Azure_AKSMinimumVersion`
- [x] `AZURE_AKS_POOL_MINIMUM_MAXPODS` instead of `Azure_AKSNodeMinimumMaxPods`
- [x] `AZURE_RESOURCE_ALLOWED_LOCATIONS` instead of `Azure_AllowedRegions`
- [x] `AZURE_APIM_MINIMUM_CERTIFICATE_LIFETIME` instead of `Azure_MinimumCertificateLifetime`