Use PoolAllocator for CCoinsMap

In my benchmarks, using this pool allocator for CCoinsMap gives about
20% faster `-reindex-chainstate` with -dbcache=5000 with practically the
same memory usage. The change in max RSS changed was 0.3%.

The `validation_flush_tests` tests need to be updated because
memory allocation is now done in large pools instead of one node at a
time, so the limits need to be updated accordingly.

1 files changed, 4 insertions, 2 deletions

diff --git a/src/coins.cpp b/src/coins.cpp
index f55932f302..0fe642e46b 100644
--- a/src/coins.cpp
+++ b/src/coins.cpp
@@ -34,7 +34,7 @@ size_t CCoinsViewBacked::EstimateSize() const { return base->EstimateSize(); }
 
 CCoinsViewCache::CCoinsViewCache(CCoinsView* baseIn, bool deterministic) :
     CCoinsViewBacked(baseIn), m_deterministic(deterministic),
-    cacheCoins(0, SaltedOutpointHasher(/*deterministic=*/deterministic))
+    cacheCoins(0, SaltedOutpointHasher(/*deterministic=*/deterministic), CCoinsMap::key_equal{}, &m_cache_coins_memory_resource)
 {}
 
 size_t CCoinsViewCache::DynamicMemoryUsage() const {
@@ -317,7 +317,9 @@ void CCoinsViewCache::ReallocateCache()
     // Cache should be empty when we're calling this.
     assert(cacheCoins.size() == 0);
     cacheCoins.~CCoinsMap();
-    ::new (&cacheCoins) CCoinsMap(0, SaltedOutpointHasher(/*deterministic=*/m_deterministic));
+    m_cache_coins_memory_resource.~CCoinsMapMemoryResource();
+    ::new (&m_cache_coins_memory_resource) CCoinsMapMemoryResource{};
+    ::new (&cacheCoins) CCoinsMap{0, SaltedOutpointHasher{/*deterministic=*/m_deterministic}, CCoinsMap::key_equal{}, &m_cache_coins_memory_resource};
 }
 
 void CCoinsViewCache::SanityCheck() const