[hle/am] make Service::Process move-only to fix #3908 KProcess use-after-free (#4137)

#3908 changed process_creation.*, CreateProcess/CreateApplicationProcess, to return std::optional<Process> instead of std::unique_ptr<Process>, so the AM sites now transfer a Process by value via make_unique<Service::Process>(*std::move(opt)).

The consequence: Process owns a refcounted KProcess* but its user-declared dtor suppressed the implicit move ctor, so that "move" silently shallow-copied and the temporary's dtor Close()/RemoveProcess()'d the shared handle -> use-after-free.

It's seems to be user end based, so whether it crashes may depend on machine, compiler, allocator reuse, refcount slack, and the AM event-observer thread race, idk. It reliably crashed my MSVC build at launching games (cstack: ProcessHolder -> MultiWait -> KSynchronizationObject::Wait -> null) multiple times.

Fix: give Process a move ctor that steals the handle (nulling the source so the moved-from dtor is a no-op) and delete copy/move-assign, making the optional<->unique_ptr transfer safe.

Bonus: explicited delete for the 3 kinds of assignment: copy ctor (the one used in eden), copy assign and move assign (currently unused) to force compile error if they ever come to use.

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/4137
Reviewed-by: Lizzie <lizzie@eden-emu.dev>
Reviewed-by: MaranBr <maranbr@eden-emu.dev>

src/core/hle/service/os/process.h

@@ -6,6 +6,8 @@
 
 #pragma once
 
+#include <utility>
+
 #include "common/common_types.h"
 
 namespace Core {
@@ -28,6 +30,15 @@ public:
     inline explicit Process(Core::System& system) noexcept : m_system(system) {}
     inline ~Process() { this->Finalize(); }
 
+    Process(const Process&) = delete;
+    Process& operator=(const Process&) = delete;
+    Process& operator=(Process&&) = delete;
+    inline Process(Process&& other) noexcept
+        : m_system(other.m_system), m_process(std::exchange(other.m_process, nullptr)),
+          m_main_thread_stack_size(std::exchange(other.m_main_thread_stack_size, 0)),
+          m_main_thread_priority(std::exchange(other.m_main_thread_priority, 0)),
+          m_process_started(std::exchange(other.m_process_started, false)) {}
+
     bool Initialize(Loader::AppLoader& loader, Loader::ResultStatus& out_load_result);
     void Finalize();