## Issue being fixed or feature implemented
This is an implementation of DIP0027 "Credit Asset Locks".
It's a mechanism to fluidly exchange between Dash and credits.
## What was done?
This pull request includes:
- Asset Lock transaction
- Asset Unlock transaction (withdrawal)
- Credit Pool in coinbase
- Unit tests for Asset Lock/Unlock tx
- New functional test `feature_asset_locks.py`
RPC: currently locked amount (credit pool) is available through rpc call
`getblock`.
## How Has This Been Tested?
There added new unit tests for basic checks of transaction validity
(asset lock/unlock).
Also added new functional test "feature_asset_locks.py" that cover
typical cases, but not all corner cases yet.
## Breaking Changes
This feature should be activated as hard-fork because:
- It adds 2 new special transaction and one of them [asset unlock tx]
requires update consensus rulels
- It adds new data in coinbase tx (credit pool)
## Checklist:
- [x] I have performed a self-review of my own code
- [x] I have commented my code, particularly in hard-to-understand areas
- [x] I have added or updated relevant unit/integration/functional/e2e
tests
- [ ] I have made corresponding changes to the documentation
**To release DIP 0027**
- [x] I have assigned this pull request to a milestone
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Co-authored-by: UdjinM6 <UdjinM6@users.noreply.github.com>
