core: TestContext2Apply_multiDepose_createBeforeDestroy incorrect logic

This test was re-using the same context to run three consecutive
plan/apply operations, which is not safe because we will accumulate more
planned changes with each change, creating duplicate entries in the diff.

Instead, to properly simulate a sequence of consecutive runs of Terraform
we must start with a fresh context each time, though still pass forward
the previous state which would in the real world be persisted via a state
manager between these runs.

terraform/context_apply_test.go

@@ -4761,6 +4761,11 @@ aws_instance.web: (2 deposed)
 	}
 
 	createdInstanceId = "qux"
+	ctx = testContext2(t, &ContextOpts{
+		Config:           m,
+		ProviderResolver: providers.ResolverFixed(ps),
+		State:            state,
+	})
 	if _, diags := ctx.Plan(); diags.HasErrors() {
 		t.Fatalf("plan errors: %s", diags.Err())
 	}
@@ -4784,6 +4789,11 @@ aws_instance.web: (1 deposed)
 	}
 
 	createdInstanceId = "quux"
+	ctx = testContext2(t, &ContextOpts{
+		Config:           m,
+		ProviderResolver: providers.ResolverFixed(ps),
+		State:            state,
+	})
 	if _, diags := ctx.Plan(); diags.HasErrors() {
 		t.Fatalf("plan errors: %s", diags.Err())
 	}