title: Bit-Field with std::byte as member type cannot be initialized
body: <p>In C++20, default member initializers for bit-fields are possible. But this feature seems impossible to use with <code>std::byte</code>. </p>
  
  <pre><code>struct Test {
      std::byte a : 2 = std::byte{0}; // NOK
      uint8_t   b : 2 = 0; // OK
  };
  </code></pre>
  
  <p>Is this intentional or a bug in g++-10 (the version I'm using).</p>