## Description 

"Trading" usually means buying and selling assets with the goal of
making profit from such transactions. Although "trading" makes some kind
of sense in the app example where we demonstrated swapping assets with
shared objects, the example is really barter or swap in nature. I
decided to rename it to convey the concept better.

## Test Plan 

Visual inspection

---
If your changes are not user-facing and do not break anything, you can
skip the following section. Otherwise, please briefly describe what has
changed under the Release Notes section.

### Type of Change (Check all that apply)

- [ ] protocol change
- [ ] user-visible impact
- [ ] breaking change for a client SDKs
- [ ] breaking change for FNs (FN binary must upgrade)
- [ ] breaking change for validators or node operators (must upgrade
binaries)
- [ ] breaking change for on-chain data layout
- [ ] necessitate either a data wipe or data migration

### Release notes

---------

Co-authored-by: Zihe Huang <zihehuang@Zihes-MacBook-Pro.local>
Co-authored-by: ronny-mysten <118224482+ronny-mysten@users.noreply.github.com>
Co-authored-by: Ronny Roland <ronmilton@mystenlabs.com>