Merge #16443: refactor: have CCoins* data managed under CChainState

582d2cd747 Cover UTXO set access with lock annotations (James O'Beirne)
5693530685 refactor: have CCoins* data managed under CChainState (James O'Beirne)
fae6ab6aed refactor: pcoinsTip -> CChainState::CoinsTip() (James O'Beirne)

Pull request description:

  This is part of the [assumeutxo project](https://github.com/bitcoin/bitcoin/projects/11):

  Parent PR: #15606
  Issue: #15605
  Specification: https://github.com/jamesob/assumeutxo-docs/tree/2019-04-proposal/proposal

  ---

  This change encapsulates UTXO set data within CChainState instances, removing global data `pcoinsTip` and `pcoinsviewdb`. This is necessary if we want to maintain multiple chainstates with their own rendering of the UTXO set.

  We introduce a class CoinsViews which consolidates the construction of a CCoins* hierarchy.

  This commit could be broken into smaller pieces, but it would require more ephemeral diffs to, e.g., temporarily change CCoinsViewDB's constructor invocations.

ACKs for top commit:
  Sjors:
    reACK 582d2cd747
  MarcoFalke:
    ACK 582d2cd747

Tree-SHA512: ec9d904fe5dca8cd2dc4b7916daa5d8bab30856dd4645987300f905e0a19f9919fce4f9d1ff03eda982943ca73e6e9a746be6cf53b46510de36e8c81a1eafba1

test/functional/feature_dbcrash.py

@@ -58,7 +58,7 @@ class ChainstateWriteCrashTest(BitcoinTestFramework):
         self.base_args = ["-limitdescendantsize=0", "-maxmempool=0", "-rpcservertimeout=900", "-dbbatchsize=200000"]
 
         # Set different crash ratios and cache sizes.  Note that not all of
-        # -dbcache goes to pcoinsTip.
+        # -dbcache goes to the in-memory coins cache.
         self.node0_args = ["-dbcrashratio=8", "-dbcache=4"] + self.base_args
         self.node1_args = ["-dbcrashratio=16", "-dbcache=8"] + self.base_args
         self.node2_args = ["-dbcrashratio=24", "-dbcache=16"] + self.base_args