Add CChainState::ResizeCoinsCaches

Also adds CCoinsViewCache::ReallocateCache() to attempt to free
memory that the cacheCoins's allocator may be hanging onto when
downsizing the cache.

Adds `CChainState::m_coins{tip,db}_cache_size_bytes` data members
so that we can reference cache size on a per-chainstate basis for
flushing.

src/init.cpp

@@ -1533,7 +1533,7 @@ bool AppInitMain(const util::Ref& context, NodeContext& node)
     int64_t nCoinDBCache = std::min(nTotalCache / 2, (nTotalCache / 4) + (1 << 23)); // use 25%-50% of the remainder for disk cache
     nCoinDBCache = std::min(nCoinDBCache, nMaxCoinsDBCache << 20); // cap total coins db cache
     nTotalCache -= nCoinDBCache;
-    nCoinCacheUsage = nTotalCache; // the rest goes to in-memory cache
+    int64_t nCoinCacheUsage = nTotalCache; // the rest goes to in-memory cache
     int64_t nMempoolSizeMax = gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000;
     LogPrintf("Cache configuration:\n");
     LogPrintf("* Using %.1f MiB for block index database\n", nBlockTreeDBCache * (1.0 / 1024 / 1024));
@@ -1645,7 +1645,7 @@ bool AppInitMain(const util::Ref& context, NodeContext& node)
                     }
 
                     // The on-disk coinsdb is now in a good state, create the cache
-                    chainstate->InitCoinsCache();
+                    chainstate->InitCoinsCache(nCoinCacheUsage);
                     assert(chainstate->CanFlushToDisk());
 
                     if (!is_coinsview_empty(chainstate)) {