provider: Support customization of all service endpoints

Historically, we have treated endpoint customization as an optional enhancement when adding service clients to the provider. Over time, the necessity of service endpoint customization has changed including:

* FIPS 140-2 compliant endpoints
* AWS C2S and SC2S potential usage
* AWS Snowball potential usage
* Local testing solutions such as LocalStack
* Rare incorrect default endpoint information provided by the AWS Go SDK

This change enables all existing service clients to support endpoint customization and going forward we can include this support by default. If the AWS Go SDK provides a better customization method in the future or defines environment variable support, we can revisit this in the future. We may also choose to further optimize endpoint handling via new provider configurations (e.g. use all known FIPS 140-2 endpoints).

Endpoint service naming is based on existing configuration. Where we do not have a prior configuration, we opt for using the AWS CLI service naming minus any hyphens. We also deprecate our own naming for `kinesis_analytics` and `r53` with `kinesisanalytics` and `route53` respectively for consistency.

References:

* https://aws.amazon.com/compliance/fips/
* https://aws.amazon.com/federal/us-intelligence-community/
* https://aws.amazon.com/snowball/
* https://docs.aws.amazon.com/cli/latest/index.html
* https://localstack.cloud/
* hashicorp#7735
* hashicorp#8007
* hashicorp#7985
* hashicorp#4967
* hashicorp#4670
* hashicorp#3941
* hashicorp#3888
* hashicorp#3608