## Issue being fixed or feature implemented
Given the hard fork that happened on testnet, there is now lots of the
transactions that were made on the fork that is no longer valid. Some
transactions could be relayed and mined again but some like coinjoin
mixing won't be relayed because of 0 fee and transactions spending
coinbases from the forked branch are no longer valid at all.
## What was done?
Introduce `wipewallettxes` RPC and `wipetxes` command for `dash-wallet`
tool to be able to get rid of some/all txes in the wallet.
## How Has This Been Tested?
run tests, use rpc/command on testnet wallet
## Breaking Changes
n/a
## Checklist:
- [x] I have performed a self-review of my own code
- [ ] I have commented my code, particularly in hard-to-understand areas
- [ ] I have added or updated relevant unit/integration/functional/e2e
tests
- [ ] I have made corresponding changes to the documentation
- [x] I have assigned this pull request to a milestone _(for repository
code-owners and collaborators only)_
