init: Correct coins db cache size setting

The chainstate caches are currently re-balanced on startup
even in the non-assumeutxo case, leading to the database being
needlessly re-opened and its cache re-allocated.

Similar to `InitCoinsCache` and `m_coinstip_cache_size_bytes` the
`m_coinsdb_cache_size_bytes` should be set in `InitCoinsDB`.

Together with only conservatively setting the cache values when a
assumeutxo chainstate is present, this allows for skipping the cache
re-balance during initialization in the normal non-assumeutxo case.

src/validation.cpp

@@ -1972,6 +1972,8 @@ void Chainstate::InitCoinsDB(
             .obfuscate = true,
             .options = m_chainman.m_options.coins_db},
         m_chainman.m_options.coins_view);
+
+    m_coinsdb_cache_size_bytes = cache_size_bytes;
 }
 
 void Chainstate::InitCoinsCache(size_t cache_size_bytes)