major refactoring: db.Player is now core.Player

- misc. cleanup
- core/db/players.go: works with core.Player types, will also grab inventory table

core/protocol/pool/pool.go

@@ -0,0 +1,19 @@
+package pool
+
+import (
+	"bytes"
+	"sync"
+)
+
+var allocator = &sync.Pool{
+	New: func() any { return new(bytes.Buffer) },
+}
+
+func Get() *bytes.Buffer {
+	return allocator.Get().(*bytes.Buffer)
+}
+
+func Put(buf *bytes.Buffer) {
+	buf.Reset()
+	allocator.Put(buf)
+}