Custom Metric Improvements

[Sharpz7]

Currently we support the following through custom metrics:

• Graf frame selection with https://github.com/radoss-org/retuve/blob/main/retuve/hip_us/multiframe/graf.py#L290
• Per-frame metrics
• Full frame metrics in 2D and 3D
• Drawing in X-Ray and Ultrasound

We need to extend this with support for

• Support for per-frame metrics in x-ray
• Support for custom handlers

We should ensure that our current metrics actually go through custom metrics:

• Alpha, Coverage, other US
• IHDI, Tonnis, other X-Ray

Other

• We should make scan-quality a first-class feature applying to 2DUS/Xray optionally and 2DSW and 3D always. Generalise it away from graf frame to best frame.