[kernel] Store object ids instead of full koids

In preparation for futexes, I wanted to make kobjects a bit lighter.
Storing 32 bits of object id, and 8 bits of type (and not ending the
class in a ushort for handle count, which meant all kobjects were likely
to have a bunch of pad bytes), the kobject class data is now just one 8
byte word.

Also from this, change logs that mention threads or processes from
printing the full koid to just 2 bytes of object id from both process
and thread, which makes following the logs much easier.

src/kernel/objects/kobject.cpp

@@ -7,30 +7,29 @@
 
 namespace obj {
 
-static j6_koid_t next_koids [static_cast<size_t>(kobject::type::max)] = { 0 };
+static constexpr unsigned types_count = static_cast<unsigned>(kobject::type::max);
+
+static uint32_t next_oids [types_count] = { 0 };
+
+static_assert(types_count <= (1 << kobject::koid_type_bits),
+        "kobject::koid_type_bits cannot represent all kobject types");
+
+static uint32_t
+oid_generate(kobject::type t)
+{
+    kassert(t < kobject::type::max, "Object type out of bounds");
+    unsigned type_int = static_cast<unsigned>(t);
+    return __atomic_fetch_add(&next_oids[type_int], 1, __ATOMIC_RELAXED);
+}
 
 kobject::kobject(type t) :
-    m_koid(koid_generate(t)),
-    m_handle_count(0)
+    m_handle_count {0},
+    m_type {t},
+    m_obj_id {oid_generate(t)}
 {}
 
 kobject::~kobject() {}
 
-j6_koid_t
-kobject::koid_generate(type t)
-{
-    kassert(t < type::max, "Object type out of bounds");
-    uint64_t type_int = static_cast<uint64_t>(t);
-    uint64_t id = __atomic_fetch_add(&next_koids[type_int], 1, __ATOMIC_SEQ_CST);
-    return (type_int << 48) | id;
-}
-
-kobject::type
-kobject::koid_type(j6_koid_t koid)
-{
-    return static_cast<type>((koid >> 48) & 0xffffull);
-}
-
 void
 kobject::on_no_handles()
 {