data: indexer processes

* TaskBuildIndex starts seperate indexer processes and communicates via shared memory
* indexer processes get restarted if they fail
* indexer processes are killed when the app closes or crashes
* added utility class SharedMemory to allocate and access shared memory, providing basic data structures
* added SharedMemoryGarbageCollector for keeping track of running instances and cleaning up shared memory in case of a crash
* show errors for source files that crashed during indexing
* added basic exception handling to task scheduling
* added option to turn off processes and use threads in preferences, but still use shared memory

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src/lib/data/indexer/interprocess/InterprocessIndexerCommandManager.h

@@ -0,0 +1,27 @@
+#ifndef INTERPROCESS_INDEXER_COMMAND_MANAGER_H
+#define INTERPROCESS_INDEXER_COMMAND_MANAGER_H
+
+#include "BaseInterprocessDataManager.h"
+#include "shared_types/SharedIndexerCommand.h"
+
+class IndexerCommand;
+
+class InterprocessIndexerCommandManager
+	: public BaseInterprocessDataManager
+{
+public:
+	InterprocessIndexerCommandManager(const std::string& instanceUuid, Id processId, bool isOwner);
+	virtual ~InterprocessIndexerCommandManager();
+
+	void setIndexerCommands(const std::vector<std::shared_ptr<IndexerCommand>>& indexerCommands);
+	std::shared_ptr<IndexerCommand> popIndexerCommand();
+
+	void clearIndexerCommands();
+	size_t indexerCommandCount();
+
+private:
+	static const char* s_sharedMemoryNamePrefix;
+	static const char* s_indexerCommandsKeyName;
+};
+
+#endif // INTERPROCESS_INDEXER_COMMAND_MANAGER_H