This issue is dedicated to keeping track of progress for the process of bringing random.cpp file up to the latest bitcoin version. It's related to #643 and aims to keep info on the WIP updated without crowding the PR with "useless" info.

• Cherry-pick bitcoin@8c1dbc5 ([Refactor] Remove begin/end_ptr functions #802)
• Merge [Crypto] Use stronger rand for key generation #643
  • Cherry-pick util: Specific GetOSRandom for Linux/FreeBSD/OpenBSD bitcoin/bitcoin#9821 (in [Crypto] Use stronger rand for key generation #643)
    • Cherry-pick bitcoin@224e6eb
    • Cherry-pick bitcoin@7cad849
    • Cherry-pick bitcoin@7e6dcd9
  • Cherry-pick Kill insecure_random and associated global state bitcoin/bitcoin#8914 (in [Crypto] Use stronger rand for key generation #643)
    • Merge [Tests] Add tests for CAddrMan #902 (Backport Creates unittests for addrman, makes addrman more testable. bitcoin/bitcoin#6720 and Adds unittests for CAddrMan and CAddrinfo, removes source of non-determinism. bitcoin/bitcoin#7212)
      • Merge [Test] Create new per-test fixtures #806 (Backport tests: add a BasicTestingSetup and apply to all tests bitcoin/bitcoin#5883 and Reinitialize state in between individual unit tests. bitcoin/bitcoin#5852)
      • Merge [Net] nLastTry is only used for addrman entries #800
      • Merge [Net] Improve addrman Select() performance when buckets are nearly empty #798
  • Cherry-pick FastRandomContext improvements and switch to ChaCha20 bitcoin/bitcoin#9792
    • Cherry-pick bitcoin@1632922
  • Cherry-pick bitcoin@97477c5
  • Cherry-pick bitcoin@f544094
  • Cherry-pick bitcoin@33f853d
  • Cherry-pick bitcoin@2c0a6f1
  • Cherry-pick bitcoin@399fb8f
  • Cherry-pick bitcoin@888cce5
  • Backport Use FastRandomContext for all tests bitcoin/bitcoin#10321
    • Cherry-pick bitcoin@37e864e
  • Cherry-pick bitcoin@cb24c85
  • Cherry-pick bitcoin@9af207c
  • Cherry-pick bitcoin@a9e82f6
  • Cherry-pick bitcoin@674848f
  • Cherry-pick bitcoin@a8ae0b2
  • Cherry-pick bitcoin@b82c55a
  • Cherry-pick bitcoin@077d01f
  • Cherry-pick bitcoin@ee2d10a
  • Cherry-pick bitcoin@8d98d42
  • Cherry-pick bitcoin@e414486
• Backport Switch all RNG code to the built-in PRNG bitcoin/bitcoin#14955
• Backport Add RNG strengthening (10ms once every minute) bitcoin/bitcoin#15224
• Backport Use RdSeed when available, and reduce RdRand load bitcoin/bitcoin#15250
• Backport test: Make bloom tests deterministic bitcoin/bitcoin#15324
• Backport Add ChaCha20 encryption option (XOR) bitcoin/bitcoin#15512
• Cherry-pick bitcoin@84f4194
• Cherry-pick bitcoin@c865ee1
• Cherry-pick bitcoin@9c4dc59
• Cherry-pick bitcoin@385ad11
• Cherry-pick bitcoin@190bf62
• Cherry-pick bitcoin@2068f08