[kernel] Add syscall helpers

Added the syscalls/helpers.h file to templatize common kobject syscall
operations. Also moved most syscall implementations to using
process::current() and thread::current() instead of asking the
scheduler.

src/kernel/objects/channel.h

@@ -14,6 +14,8 @@ public:
 	channel();
 	virtual ~channel();
 
+	static constexpr kobject::type type = kobject::type::channel;
+
 	/// Check if the channel has space for a message to be sent
 	inline bool can_send() const { return check_signal(j6_signal_channel_can_send); }
 

src/kernel/objects/endpoint.h

@@ -13,6 +13,8 @@ public:
 	endpoint();
 	virtual ~endpoint();
 
+	static constexpr kobject::type type = kobject::type::endpoint;
+
 	/// Close the endpoint, waking all waiting processes with an error
 	void close();
 

src/kernel/objects/event.h

@@ -10,4 +10,6 @@ class event :
 public:
 	event() :
 		kobject(type::event) {}
+
+	static constexpr kobject::type type = kobject::type::event;
 };

src/kernel/objects/process.h

@@ -24,6 +24,8 @@ public:
 	/// Destructor.
 	virtual ~process();
 
+	static constexpr kobject::type type = kobject::type::process;
+
 	/// Get the currently executing process.
 	static process & current();
 

src/kernel/objects/thread.h

@@ -50,6 +50,8 @@ public:
 	/// Destructor
 	virtual ~thread();
 
+	static constexpr kobject::type type = kobject::type::thread;
+
 	/// Get the currently executing thread.
 	static thread & current();
 

src/kernel/objects/vm_area.h

@@ -38,6 +38,8 @@ public:
 	vm_area(size_t size, vm_flags flags = vm_flags::none);
 	virtual ~vm_area();
 
+	static constexpr kobject::type type = kobject::type::vma;
+
 	/// Get the current virtual size of the memory area
 	size_t size() const { return m_size; }