[NFC] Make headers self-contained.

[rupprecht]

Summary

Some headers in LLDB work only when considered as textual inclusion, but not if one attempts to use them on their own or with a different context.

• python-typemaps.h: uses Python definitions without using "Python.h".
• RISCVCInstructions.h uses RISC-V register enums without including the enums header.
• RISCVInstructions.h includes EmulateInstructionRISCV.h, but is unnecessary since we forward-declare EmulateInstructionRISCV anyway. Including the header is problematic because EmulateInstructionRISCV.h uses DecodeResult which isn't defined until later in RISCVInstructions.h.

This makes LLDB build cleanly with the "parse_headers" feature [1]. I'm not sure what the analagous CMake option is.

[1] I didn't find public documentation but @MaskRay wrote this up: https://maskray.me/blog/2022-09-25-layering-check-with-clang#parse_headers

[MaskRay]

lldb/source/Plugins/Instruction/RISCV/RISCVInstructions.h

15–16

I assume that this is correct, even after considering IWYU. Perhaps worth a double check.

[rupprecht]

lldb/source/Plugins/Instruction/RISCV/RISCVInstructions.h

15–16

Thanks, I double checked: the only top-level type exported by EmulateInstructionRISCV.h is class EmulateInstructionRISCV. That's forward-declared in this file (line 20 on the base side), and only ever referred to by reference, so a forward declare is fully sufficient for that.

lldb/bindings/python/python-typemaps.h

 #ifndef LLDB_BINDINGS_PYTHON_PYTHON_TYPEMAPS_H
 #define LLDB_BINDINGS_PYTHON_PYTHON_TYPEMAPS_H
 
+#include <Python.h>
+
 // Defined here instead of a .swig file because SWIG 2 doesn't support
 // explicit deleted functions.
 struct Py_buffer_RAII {
   Py_buffer buffer = {};
   Py_buffer_RAII(){};
   Py_buffer &operator=(const Py_buffer_RAII &) = delete;
   Py_buffer_RAII(const Py_buffer_RAII &) = delete;
   ~Py_buffer_RAII() {
     if (buffer.obj)
       PyBuffer_Release(&buffer);
   }
 };
 
 #endif // LLDB_BINDINGS_PYTHON_PYTHON_TYPEMAPS_H

lldb/source/Plugins/Instruction/RISCV/RISCVCInstructions.h

 //===-- RISCVCInstructions.h ----------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLDB_SOURCE_PLUGINS_INSTRUCTION_RISCV_RISCVCINSTRUCTION_H
 #define LLDB_SOURCE_PLUGINS_INSTRUCTION_RISCV_RISCVCINSTRUCTION_H
 
 #include <cstdint>
 #include <variant>
 
+#include "Plugins/Process/Utility/lldb-riscv-register-enums.h"
 #include "RISCVInstructions.h"
 #include "llvm/ADT/Optional.h"
 
 namespace lldb_private {
 
 /// Unified RISC-V C register encoding.
 struct RxC {
   uint32_t rd;

lldb/source/Plugins/Instruction/RISCV/RISCVInstructions.h

 //===-- RISCVInstructions.h -----------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLDB_SOURCE_PLUGINS_INSTRUCTION_RISCV_RISCVINSTRUCTION_H
 #define LLDB_SOURCE_PLUGINS_INSTRUCTION_RISCV_RISCVINSTRUCTION_H
 
 #include <cstdint>
 #include <variant>
 
-#include "EmulateInstructionRISCV.h"
 #include "llvm/ADT/APFloat.h"
 #include "llvm/ADT/Optional.h"
 
 namespace lldb_private {
 
 class EmulateInstructionRISCV;
 
 struct Rd {
   uint32_t rd;