Make testing execution operations, messages and queries less verbose

[jvff]

Motivation

Executing operations, messages and queries in tests requires some setup that ends up being repeated in many tests. This reduces readability, since most of that is boilerplate code.

Proposal

Add some test helper types, functions or methods to simplify the code in the tests.

One idea might be to use a builder pattern:

execution_state_view
    .execute_test_operation(app_id, operation)
    .with_authenticated_signer(owner)
    .await?;