feat: PDB import via RawPDB, no msdia140.dll dependency

Replace DIA SDK COM-based PDB importer with RawPDB (MolecularMatters)
which reads PDB files directly via memory-mapped I/O. Adds File menu
"Import PDB..." dialog with type filtering, selection, and progress.

- Vendor raw_pdb into third_party/
- Two-phase API: enumeratePdbTypes() + importPdbSelected()
- Full recursive import of structs/unions/arrays/pointers/bitfields
- PDB import dialog with name filter, select-all, type count
- Benchmark: 1654 types from ntkrnlmp.pdb in 16ms
- Reorganize import/export files into src/imports/

third_party/raw_pdb/src/PDB_SourceFileStream.h

@@ -0,0 +1,65 @@
+// Copyright 2011-2022, Molecular Matters GmbH <office@molecular-matters.com>
+// See LICENSE.txt for licensing details (2-clause BSD License: https://opensource.org/licenses/BSD-2-Clause)
+
+#pragma once
+
+#include "Foundation/PDB_Macros.h"
+#include "Foundation/PDB_ArrayView.h"
+#include "PDB_CoalescedMSFStream.h"
+
+
+namespace PDB
+{
+	class PDB_NO_DISCARD DirectMSFStream;
+
+
+	class PDB_NO_DISCARD SourceFileStream
+	{
+	public:
+		SourceFileStream(void) PDB_NO_EXCEPT;
+		explicit SourceFileStream(const DirectMSFStream& directStream, uint32_t size, uint32_t offset) PDB_NO_EXCEPT;
+
+		PDB_DEFAULT_MOVE(SourceFileStream);
+
+		// Returns the number of modules.
+		PDB_NO_DISCARD inline uint32_t GetModuleCount(void) const PDB_NO_EXCEPT
+		{
+			return m_moduleCount;
+		}
+
+		// Returns a view of all the filename offsets for the module with the given index.
+		PDB_NO_DISCARD inline ArrayView<uint32_t> GetModuleFilenameOffsets(size_t moduleIndex) const PDB_NO_EXCEPT
+		{
+			const uint16_t moduleStartIndex = m_moduleIndices[moduleIndex];
+			const uint16_t moduleFileCount = m_moduleFileCounts[moduleIndex];
+			
+			return ArrayView<uint32_t>(m_fileNameOffsets + moduleStartIndex, moduleFileCount);
+		}
+
+		// Returns a filename for the given filename offset.
+		PDB_NO_DISCARD inline const char* GetFilename(uint32_t filenameOffset) const PDB_NO_EXCEPT
+		{
+			return m_stringTable + filenameOffset;
+		}
+
+	private:
+		CoalescedMSFStream m_stream;
+
+		// the number of modules
+		uint32_t m_moduleCount;
+
+		// the indices into the file name offsets, for each module
+		const uint16_t* m_moduleIndices;
+
+		// the number of files, for each module
+		const uint16_t* m_moduleFileCounts;
+
+		// the filename offsets into the string table, for all modules
+		const uint32_t* m_fileNameOffsets;
+
+		// the string table storing all filenames
+		const char* m_stringTable;
+
+		PDB_DISABLE_COPY(SourceFileStream);
+	};
+}