3.5.1.0 release candidate

[grigzy28]

Issue being fixed or feature implemented

Operating system upgrades and unable to build on newer systems plus several other enhancements and fixes

Allows building on newer operating system and also improves resource usage

What was done?

Some memory optimizations
Improved startup times
Introduced contributions cleanup code from Dash code
Changed some logging functions to reduce debug log writes
Created a GETBLOCKCOUNT buffer variable to increase the speed of getblockcount rpc calls
Created RPC calls for only enabled masternode lists for speed of the StakeCube systems

FIX: Major updates to dependencies and internal support dependencies for building on newer operating systems
FIX: deadlock(race condition) on an RPC call that would completely lock up the wallet if queried from the wallet too fast
FIX: Introduced a routine to validate consensus rules faster for quicker startup times

Update: Added some checkpoint entries

How Has This Been Tested?

Ran for many, many months on own systems and finally on "Earn" systems over the past month(s)

Breaking Changes

All that have been discovered so far have been corrected

Checklist:

• 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

For repository code-owners and collaborators only

• I have assigned this pull request to a milestone