echoprovider: Add a new test-only v6 provider that echoes ephemeral provider data

.changes/unreleased/FEATURES-20241111-165312.yaml

@@ -0,0 +1,6 @@
+kind: FEATURES
+body: 'echoprovider: Introduced new `echoprovider` package, which contains a v6 Terraform
+  provider that can be used to test ephemeral resource data.'
+time: 2024-11-11T16:53:12.399802-05:00
+custom:
+  Issue: "389"

.changes/unreleased/NOTES-20241111-165206.yaml

@@ -0,0 +1,6 @@
+kind: NOTES
+body: 'echoprovider: The `echoprovider` package is considered experimental and may
+  be altered or removed in a subsequent release'
+time: 2024-11-11T16:52:06.287978-05:00
+custom:
+  Issue: "389"

.github/workflows/ci-go.yml

@@ -39,7 +39,7 @@ jobs:
           terraform_version: ${{ matrix.terraform }}
           terraform_wrapper: false
       - run: go mod download
-      - run: go test -coverprofile=coverage.out ./...
+      - run: go test -v -coverprofile=coverage.out ./...
         env:
           TF_ACC: "1"
       - name: Remove wildcard suffix from TF version

echoprovider/doc.go

@@ -0,0 +1,20 @@
+// Copyright (c) HashiCorp, Inc.
+// SPDX-License-Identifier: MPL-2.0
+
+// Package echoprovider contains a protocol v6 Terraform provider that can be used to transfer data from
+// provider configuration to state via a managed resource. This is only meant for provider acceptance testing
+// of data that cannot be stored in Terraform artifacts (plan/state), such as an ephemeral resource.
+//
+// Example Usage:
+//
+//	// Ephemeral resource that is under test
+//	ephemeral "examplecloud_thing" "this" {
+//		name = "thing-one"
+//	}
+//
+//	provider "echo" {
+//		data = ephemeral.examplecloud_thing.this
+//	}
+//
+//	resource "echo" "test" {} // The `echo.test.data` attribute will contain the ephemeral data from `ephemeral.examplecloud_thing.this`
+package echoprovider