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_ModuleLineStream.cpp

@@ -0,0 +1,31 @@
+// 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)
+
+#include "PDB_PCH.h"
+#include "PDB_ModuleLineStream.h"
+#include "PDB_RawFile.h"
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::ModuleLineStream::ModuleLineStream(void) PDB_NO_EXCEPT
+	: m_stream(), m_c13LineInfoOffset(0)
+{
+}
+
+
+// ------------------------------------------------------------------------------------------------
+// ------------------------------------------------------------------------------------------------
+PDB::ModuleLineStream::ModuleLineStream(const RawFile& file, uint16_t streamIndex, uint32_t streamSize, size_t c13LineInfoOffset) PDB_NO_EXCEPT
+	: m_stream(file.CreateMSFStream<CoalescedMSFStream>(streamIndex, streamSize)), m_c13LineInfoOffset(c13LineInfoOffset)
+{
+	// https://llvm.org/docs/PDB/ModiStream.html
+	// struct ModiStream {
+	//	uint32_t Signature;
+	//	uint8_t Symbols[SymbolSize - 4];
+	//	uint8_t C11LineInfo[C11Size];
+	//	uint8_t C13LineInfo[C13Size];
+	//	uint32_t GlobalRefsSize;
+	//	uint8_t GlobalRefs[GlobalRefsSize];
+	// };
+}