Added ephemeral http resource

[danilobuerger]

Related Issue

Fixes #508

Description

• Changed the testing to proto v6 provider server in order to utilize the echo provider (see https://developer.hashicorp.com/terraform/plugin/testing/acceptance-tests/ephemeral-resources)
• Moved the logic from data_source_http.go/Read to its own function doRequest to be shared with the new ephemeral resource
• Copied over the schema from data_source_http.go (no good way to share it since they are different structs)
• Added just one test to the new ephemeral resource to prove its working as everything is already being tested through the data source.

Rollback Plan

• If a change needs to be reverted, we will roll out an update to the code within 7 days.

Changes to Security Controls

Are there any changes to security controls (access controls, encryption, logging) in this pull request? If so, explain.