cli: Fix state migration remote version check

Previously the state migration process was using the fallback strict
error check when migrating to or from a Terraform Cloud workspace. This
resulted in an error when running init if the local and remote Terraform
versions did not exactly match.

This was excessively strict. When migrating from a remote Terraform
Cloud workspace to local state, there is no need for a version check at
all, as we cannot break the Terraform Cloud workspace. When migrating
to Terraform Cloud, we should use the more forgiving check, rather than
the strict equality.

This commit fixes both of these cases accordingly, and allows migrating
state to and from Terraform Cloud remote workspaces without errors.

command/meta_backend_migrate.go

@@ -70,6 +70,19 @@ func (m *Meta) backendMigrateState(opts *backendMigrateOpts) error {
 	opts.twoEnv = backend.DefaultStateName
 	opts.force = m.forceInitCopy
 
+	// Disregard remote Terraform version for the state source backend. If it's a
+	// Terraform Cloud remote backend, we don't care about the remote version,
+	// as we are migrating away and will not break a remote workspace.
+	m.ignoreRemoteBackendVersionConflict(opts.One)
+
+	// Check the remote Terraform version for the state destination backend. If
+	// it's a Terraform Cloud remote backend, we want to ensure that we don't
+	// break the workspace by uploading an incompatible state file.
+	diags := m.remoteBackendVersionCheck(opts.Two, opts.twoEnv)
+	if diags.HasErrors() {
+		return diags.Err()
+	}
+
 	// Determine migration behavior based on whether the source/destination
 	// supports multi-state.
 	switch {