blocks/blockstore: add CacheOpts - structure of cache config

License: MIT
Signed-off-by: Jakub Sztandera <kubuxu@protonmail.ch>

blocks/blockstore/caching.go

+package blockstore
+
+// Next to each option is it aproximate memory usage per unit
+type CacheOpts struct {
+	HasBloomFilterSize   int // 1 bit
+	HasBloomFilterHashes int // No size, 7 is usually best, consult bloom papers
+	HasARCCacheSize      int // 32 bytes
+}
+
+func DefaultCacheOpts() CacheOpts {
+	return CacheOpts{
+		HasBloomFilterSize:   512 * 8 * 1024,
+		HasBloomFilterHashes: 7,
+		HasARCCacheSize:      64 * 1024,
+	}
+}