kernel: Move non-kernel db cache size constants

These have nothing to do with the txdb, so move them out and into the
node caches.

Author: TheCharlatan

src/node/caches.cpp

@@ -12,16 +12,23 @@
 #include <algorithm>
 #include <string>
 
+// Unlike for the UTXO database, for the txindex scenario the leveldb cache make
+// a meaningful difference: https://github.com/bitcoin/bitcoin/pull/8273#issuecomment-229601991
+//! Max memory allocated to tx index DB specific cache in MiB.
+static constexpr int64_t MAX_TX_INDEX_CACHE{1024};
+//! Max memory allocated to all block filter index caches combined in MiB.
+static constexpr int64_t MAX_FILTER_INDEX_CACHE{1024};
+
 namespace node {
 CacheSizes CalculateCacheSizes(const ArgsManager& args, size_t n_indexes)
 {
     int64_t nTotalCache = (args.GetIntArg("-dbcache", nDefaultDbCache) << 20);
     nTotalCache = std::max(nTotalCache, nMinDbCache << 20); // total cache cannot be less than nMinDbCache
     IndexCacheSizes sizes;
-    sizes.tx_index = std::min(nTotalCache / 8, args.GetBoolArg("-txindex", DEFAULT_TXINDEX) ? nMaxTxIndexCache << 20 : 0);
+    sizes.tx_index = std::min(nTotalCache / 8, args.GetBoolArg("-txindex", DEFAULT_TXINDEX) ? MAX_TX_INDEX_CACHE << 20 : 0);
     nTotalCache -= sizes.tx_index;
     if (n_indexes > 0) {
-        int64_t max_cache = std::min(nTotalCache / 8, max_filter_index_cache << 20);
+        int64_t max_cache = std::min(nTotalCache / 8, MAX_FILTER_INDEX_CACHE << 20);
         sizes.filter_index = max_cache / n_indexes;
         nTotalCache -= sizes.filter_index * n_indexes;
     }

src/node/caches.h

@@ -8,14 +8,13 @@
 #include <kernel/caches.h>
 
 #include <cstddef>
-#include <cstdint>
 
 class ArgsManager;
 
 namespace node {
 struct IndexCacheSizes {
-    int64_t tx_index{0};
-    int64_t filter_index{0};
+    size_t tx_index{0};
+    size_t filter_index{0};
 };
 struct CacheSizes {
     IndexCacheSizes index;

src/txdb.h

@@ -27,12 +27,6 @@ static const int64_t nDefaultDbCache = 450;
 static const int64_t nDefaultDbBatchSize = 16 << 20;
 //! min. -dbcache (MiB)
 static const int64_t nMinDbCache = 4;
-// Unlike for the UTXO database, for the txindex scenario the leveldb cache make
-// a meaningful difference: https://github.com/bitcoin/bitcoin/pull/8273#issuecomment-229601991
-//! Max memory allocated to tx index DB specific cache in MiB.
-static const int64_t nMaxTxIndexCache = 1024;
-//! Max memory allocated to all block filter index caches combined in MiB.
-static const int64_t max_filter_index_cache = 1024;
 
 //! User-controlled performance and debug options.
 struct CoinsViewOptions {