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_ImageSectionStream.h

@@ -0,0 +1,42 @@
+// 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_Types.h"
+#include "PDB_CoalescedMSFStream.h"
+
+
+namespace PDB
+{
+	class RawFile;
+	struct IMAGE_SECTION_HEADER;
+
+
+	class PDB_NO_DISCARD ImageSectionStream
+	{
+	public:
+		ImageSectionStream(void) PDB_NO_EXCEPT;
+		explicit ImageSectionStream(const RawFile& file, uint16_t streamIndex) PDB_NO_EXCEPT;
+
+		PDB_DEFAULT_MOVE(ImageSectionStream);
+
+		// Converts a one-based section offset into an RVA.
+		PDB_NO_DISCARD uint32_t ConvertSectionOffsetToRVA(uint16_t oneBasedSectionIndex, uint32_t offsetInSection) const PDB_NO_EXCEPT;
+
+		// Returns a view of all the sections in the stream.
+		PDB_NO_DISCARD inline ArrayView<IMAGE_SECTION_HEADER> GetImageSections(void) const PDB_NO_EXCEPT
+		{
+			return ArrayView<IMAGE_SECTION_HEADER>(m_headers, m_count);
+		}
+
+	private:
+		CoalescedMSFStream m_stream;
+		const IMAGE_SECTION_HEADER* m_headers;
+		size_t m_count;
+
+		PDB_DISABLE_COPY(ImageSectionStream);
+	};
+}