kernel: Add import blocks function to C header

Add `btck_import_blocks` to import block data and rebuild indexes. The
function can either reindex all existing block files if the indexes were
previously wiped through the chainstate manager options, or import
blocks from specified file paths.

src/kernel/bitcoinkernel.cpp

@@ -795,6 +795,24 @@ void btck_chainstate_manager_destroy(btck_ChainstateManager* chainman)
     delete chainman;
 }
 
+int btck_chainstate_manager_import_blocks(btck_ChainstateManager* chainman, const char** block_file_paths_data, size_t* block_file_paths_lens, size_t block_file_paths_data_len)
+{
+    try {
+        std::vector<fs::path> import_files;
+        import_files.reserve(block_file_paths_data_len);
+        for (uint32_t i = 0; i < block_file_paths_data_len; i++) {
+            if (block_file_paths_data[i] != nullptr) {
+                import_files.emplace_back(std::string{block_file_paths_data[i], block_file_paths_lens[i]}.c_str());
+            }
+        }
+        node::ImportBlocks(*btck_ChainstateManager::get(chainman).m_chainman, import_files);
+    } catch (const std::exception& e) {
+        LogError("Failed to import blocks: %s", e.what());
+        return -1;
+    }
+    return 0;
+}
+
 btck_Block* btck_block_create(const void* raw_block, size_t raw_block_length)
 {
     auto block{std::make_shared<CBlock>()};