fix: enable the mn_rr hard fork in v20 so that a v20.1 in the future may activate mn_rr (dashpay#5699)

## Issue being fixed or feature implemented
mn_rr should be backwards compatible to v20.0.0; in the case we need to
introduce breaking changes on any of the features in mn_rr then we
should create a new mn_rr_v2 hard fork.

## What was done?
Add timestamps for mn_rr for main net activation

## How Has This Been Tested?


## Breaking Changes
None

## Checklist:
_Go over all the following points, and put an `x` in all the boxes that
apply._
- [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)_

---------

Co-authored-by: UdjinM6 <[email protected]>
Co-authored-by: Konstantin Akimov <[email protected]>

Author: 3 people

src/chainparams.cpp

@@ -214,10 +214,10 @@ class CMainParams : public CChainParams {
         consensus.vDeployments[Consensus::DEPLOYMENT_V20].nFalloffCoeff = 5;            // this corresponds to 10 periods
 
         consensus.vDeployments[Consensus::DEPLOYMENT_MN_RR].bit = 10;
-        consensus.vDeployments[Consensus::DEPLOYMENT_MN_RR].nStartTime = 19999999999;   // TODO: To be determined later
-        consensus.vDeployments[Consensus::DEPLOYMENT_MN_RR].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;
+        consensus.vDeployments[Consensus::DEPLOYMENT_MN_RR].nStartTime = 1704067200;   // January 1, 2024
+        consensus.vDeployments[Consensus::DEPLOYMENT_MN_RR].nTimeout = 1767225600; // January 1, 2026
         // NOTE: nWindowSize for MN_RR __MUST__ be greater than or equal to nSuperblockMaturityWindow for CSuperblock::GetPaymentsLimit() to work correctly
-        consensus.vDeployments[Consensus::DEPLOYMENT_MN_RR].nWindowSize = 4032; // TODO to be determined before v20 release: choose nWindowSize/nThresholdStart/nThresholdMin
+        consensus.vDeployments[Consensus::DEPLOYMENT_MN_RR].nWindowSize = 4032;
         consensus.vDeployments[Consensus::DEPLOYMENT_MN_RR].nThresholdStart = 3226;     // 80% of 4032
         consensus.vDeployments[Consensus::DEPLOYMENT_MN_RR].nThresholdMin = 2420;       // 60% of 4032
         consensus.vDeployments[Consensus::DEPLOYMENT_MN_RR].nFalloffCoeff = 5;          // this corresponds to 10 periods