Ensure all health check fields can be set from all registration points

#### Ensure all health check fields can be set from all registration points

There are many ways to register healthchecks. These are outlined below, with a type of artifact that can be used to test these cases. Each artifact may have 2 or 3 permutations, to validate `snake_case`, `CamelCase`, and maybe as a stretch, add `kebob-case` to make sure we're not breaking things needlessly.

`consul service register`
Use same file from the config file example
`curl .../agent/catalog/register`
Curl with JSON Payload w/healthcheck
`curl .../agent/check/register`
Curl with JSON Payload w/HC
`curl .../agent/service/register`
Curl with JSON Payload w/HC
A config file in `-data-dir .../`
Service level validation

Check level validation

An additional step that would be valuable is updating the documentation payloads to reflect the correct cases and all the options available per payload.

Notes: May want to update documentation to state "Payload Params" rather than "params"

###Related Issues:
https://github.com/hashicorp/consul/issues/6923
https://github.com/hashicorp/consul/issues/7566
https://github.com/hashicorp/consul/issues/7869
(https://github.com/hashicorp/consul/issues/7764)
https://github.com/hashicorp/consul/pull/7768

Compare the health-check registration paths named in the issue: consul service register, the catalog, check, and service registration endpoints, and data-directory config files. Verify which health-check fields each payload accepts across the requested naming variants, then update the corresponding documentation payloads and validation coverage; the related issues and pull request provide prior context.

Written by the indexing model from the issue text.