core: Add support for proper SeedDB import

This now merges the SeedDB to import with the one already existing

src/core/ncch/seed_db.h

@@ -0,0 +1,54 @@
+// Copyright 2018 Citra Emulator Project / 2020 Pengfei Zhu
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+// Modified from Citra's implementation to allow multiple instances
+
+#include <array>
+#include <optional>
+#include <vector>
+#include "common/common_types.h"
+#include "common/swap.h"
+
+namespace Core {
+
+constexpr std::size_t SEEDDB_PADDING_BYTES{12};
+
+struct Seed {
+    using Data = std::array<u8, 16>;
+
+    u64_le title_id;
+    Data data;
+    std::array<u8, 8> reserved;
+};
+
+class SeedDB {
+public:
+    bool Load(const std::string& path);
+    bool Save(const std::string& path);
+
+    void Add(const Seed& seed);
+    std::size_t Size() const;
+    std::optional<Seed::Data> Get(u64 title_id) const;
+
+    auto begin() {
+        return seeds.begin();
+    }
+
+    auto begin() const {
+        return seeds.begin();
+    }
+
+    auto end() {
+        return seeds.end();
+    }
+
+    auto end() const {
+        return seeds.end();
+    }
+
+private:
+    std::vector<Seed> seeds;
+};
+
+} // namespace Core