Meta issue to track changes for adding plugin and LLVM_BUILD_LLVM_DYLIB support for Windows

[fsfod]

This is meta issue to track adding support for building LLVM and Clang as a shared library on windows and to also allow the use on plugins. This will mostly be achieved by adding explicit visibility macros to public API surface that will dllexport'ed. These changes will also benefit non windows platforms by reducing the numbers of exported symbols when the default symbol visibility is set to hidden at a latter time.

Some rational for these changes is explained in this old LLVM discourse post Supporting LLVM_BUILD_LLVM_DYLIB on Windows.

LLVM

• Initial changes for llvm shared library build using explicit visibility annotations #96630
• [TableGen] Add explicit symbol visibility macros to code generated #107873
• [llvm] Support llvm::Any across shared libraries on windows #108051
• Reland 'Update llvm::Registry to work for LLVM shared library builds on windows' (#109024) #112640
• [Object][NFC] Add extern template declarations needed by llvm-objdump #109156
• [X86] Switch to the new symbol visibility macros #109982
• Add visibility macros for Target initialize function declarations both c and cpp versions needed by llvm-c tests.
• Add symbol visibility macros to abi-breaking.h.cmake #110898
• Add explicit symbol visibility macros to InstrProfData.inc #110732
• [Support] Include Support/thread.h before api implementations #111175.
• [llvm] Add explicit visibility macros to YAMLTraits classes #111484
• [SandboxIR] Add extern templates for GlobalWithNodeAPI #111940
• [llvm] Enable building Analysis plugins on windows #112303
• [Minidump] Add extern template declarations for MinidumpFile::getListStream #112568
• [DebugInfo] Fix missing includes in two headers #112766
• Always export ExecutionEngine TargetProcess functions.
• Manual visibility macros for explicit function template instantiations in LLVM
• Clang tooling generated visibility macros for LLVM.
• clang-cl template dllexport workaround.
• Default symbol visibility on non windows platforms set to hidden.
• MSVC deleted and defaulted class members changes.
• MSVC dllexport ilist fix or default template argument workaround.
• MSVC dllexport cl::opt fix or workaround.

Clang

• [Clang] Add explicit visibility symbol macros #108276
• [Clang][TableGen] Add explicit symbol visibility macros to code generated #109362
• [clang-tools-extra] Fix add_clang_library usage #109321
• [Clang] Change Attribute plugin to link clang-cpp like other examples #109319
• [Clang] Update Interpreter tests to use clang_target_link_libraries #110154
• [Clang][ASTMatchers] Add visibility macros to variables declared by macros #110206
• [clangd] Update clangDaemonTweaks to set symbol visibility macros #112304
• Sketch of clang tooling generated visibility macros for Clang Clang tooling generated visibility macros for Clang  #109702
• MSVC deleted and defaulted class members changes.