cloud: Support interop from 0.14 to 1.1

The previous conservative guarantee that we would not make backwards
incompatible changes to the state file format until at least Terraform
1.1 can now be extended. Terraform 0.14 through 1.1 will be able to
interoperably use state files, so we can update the remote backend
version compatibility check accordingly.

This is a port of https://github.com/hashicorp/terraform/pull/29645

internal/cloud/backend.go

@@ -940,9 +940,9 @@ func (b *Cloud) VerifyWorkspaceTerraformVersion(workspaceName string) tfdiags.Di
 		// are aware of are:
 		//
 		// - 0.14.0 is guaranteed to be compatible with versions up to but not
-		//   including 1.1.0
-		v110 := version.Must(version.NewSemver("1.1.0"))
-		if tfversion.SemVer.LessThan(v110) && remoteVersion.LessThan(v110) {
+		//   including 1.2.0
+		v120 := version.Must(version.NewSemver("1.2.0"))
+		if tfversion.SemVer.LessThan(v120) && remoteVersion.LessThan(v120) {
 			return diags
 		}
 		// - Any new Terraform state version will require at least minor patch

internal/cloud/backend_test.go

@@ -896,7 +896,8 @@ func TestCloud_VerifyWorkspaceTerraformVersion(t *testing.T) {
 		{"0.14.0", "0.13.5", false, false},
 		{"0.14.0", "0.14.1", true, false},
 		{"0.14.0", "1.0.99", true, false},
-		{"0.14.0", "1.1.0", true, true},
+		{"0.14.0", "1.1.0", true, false},
+		{"0.14.0", "1.2.0", true, true},
 		{"1.2.0", "1.2.99", true, false},
 		{"1.2.0", "1.3.0", true, true},
 		{"0.15.0", "latest", true, false},