validation: Use span for ImportBlocks paths

Makes it friendlier for potential future users of the kernel library if
they do not store the headers in a std::vector, but can guarantee
contiguous memory.

src/node/blockstorage.cpp

@@ -1210,7 +1210,7 @@ public:
     }
 };
 
-void ImportBlocks(ChainstateManager& chainman, std::vector<fs::path> vImportFiles)
+void ImportBlocks(ChainstateManager& chainman, std::span<const fs::path> import_paths)
 {
     ImportingNow imp{chainman.m_blockman.m_importing};
 
@@ -1245,7 +1245,7 @@ void ImportBlocks(ChainstateManager& chainman, std::vector<fs::path> vImportFile
     }
 
     // -loadblock=
-    for (const fs::path& path : vImportFiles) {
+    for (const fs::path& path : import_paths) {
         AutoFile file{fsbridge::fopen(path, "rb")};
         if (!file.IsNull()) {
             LogPrintf("Importing blocks file %s...\n", fs::PathToString(path));

src/node/blockstorage.h

@@ -29,6 +29,7 @@
 #include <memory>
 #include <optional>
 #include <set>
+#include <span>
 #include <string>
 #include <unordered_map>
 #include <utility>
@@ -429,7 +430,7 @@ public:
     void CleanupBlockRevFiles() const;
 };
 
-void ImportBlocks(ChainstateManager& chainman, std::vector<fs::path> vImportFiles);
+void ImportBlocks(ChainstateManager& chainman, std::span<const fs::path> import_paths);
 } // namespace node
 
 #endif // BITCOIN_NODE_BLOCKSTORAGE_H