[Tech]: Liquidity proxy + TBC pallets enhancements

[bragov4ik]

Problem statement

While working on #876 we found out a few minor problems with the pallets:

1. Variable/fields naming in TBC pallet is out of date
2. Buy back and burn is hard to observe externally (for users & explorers)
3. Exchange event is not always produced when exchange happens

Description

No response

Definition of Done

• [x] TBC naming is fixed (corresponds to the wiki)
• [ ] Migrations are ready (names of the tech accounts are changed)
• [ ] Event of BBB is created and produced, where applicable
• [x] Exchange event is triggered on each exchange (via liquidity_proxy)

Requirements

No response