[Feature] Support Synthetics APIs as Terraform resources

[BenB196]

Is your feature request related to a problem? Please describe.

I would like to be able to programmatically manage Elastic Synthetics via Terraform.

Describe the resource you would like to have implemented.

elastic/kibana#169547 recently introduced public APIs for these resources.

Describe the solution you'd like

This Terraform provider to be able to manage Synthetics resources.

Describe alternatives you've considered

Hacking something together via https://registry.terraform.io/providers/Mastercard/restapi/latest/docs

Additional context

elastic/cloud-on-k8s#7724

[russellproud]

Coming here to add some support to this request.

Utilising the mastercard/restapi provider works for create and update, but is unable to manage the delete lifecycle as a result of the DELETE endpoint for Synthetics requires the Id to be included in the request body, not the uri.

@BenB196 have you found a method to achieve the delete via mastercard/restapi?

[tobio]

Duplicates #335

[mholttech]

love the progress here. Any plans to expand for icmp and browser monitor types?