[Feat request] G.all_edges support order='dst'

## 🚀 Feature

When using G.all_edges, only 3 types of ordering are supported: None, 'eid', 'srcdst'.
Request: Add the option order='dst', if it is easy to do so.

## Motivation

I need to calculate:
```
uid, vid = G.all_edges(form='uv', order=None, etype=etype)
unique_vid = torch.unique(vid)
```
But torch.unique is 20% of the computation of my whole function, and torch.unique_consecutive is 10x faster.
torch.unique_consecutive assumes that the vector is already sorted, so if G.all_edges could already provide sorted vid at minimal cost, the function would be 18% faster.

## Additional context

I couldn't find the documentation of G.all_edges in the website for versions after 0.6.x.