Kernel: Remove the kmalloc_eternal heap :^)

This was a premature optimization from the early days of SerenityOS.
The eternal heap was a simple bump pointer allocator over a static
byte array. My original idea was to avoid heap fragmentation and improve
data locality, but both ideas were rooted in cargo culting, not data.

We would reserve 4 MiB at boot and only ended up using ~256 KiB, wasting
the rest.

This patch replaces all kmalloc_eternal() usage by regular kmalloc().

Kernel/Devices/ConsoleDevice.h

@@ -13,7 +13,6 @@
 namespace Kernel {
 
 class ConsoleDevice final : public CharacterDevice {
-    AK_MAKE_ETERNAL
     friend class DeviceManagement;
 
 public:

Kernel/Devices/DeviceManagement.h

@@ -24,7 +24,6 @@
 namespace Kernel {
 
 class DeviceManagement {
-    AK_MAKE_ETERNAL;
 
 public:
     DeviceManagement();

Kernel/Devices/FullDevice.h

@@ -11,7 +11,6 @@
 namespace Kernel {
 
 class FullDevice final : public CharacterDevice {
-    AK_MAKE_ETERNAL
     friend class DeviceManagement;
 
 public:

Kernel/Devices/HID/HIDManagement.h

@@ -31,7 +31,6 @@ class KeyboardClient;
 class HIDManagement {
     friend class KeyboardDevice;
     friend class MouseDevice;
-    AK_MAKE_ETERNAL;
 
 public:
     HIDManagement();

Kernel/Devices/KCOVDevice.h

@@ -11,7 +11,6 @@
 
 namespace Kernel {
 class KCOVDevice final : public BlockDevice {
-    AK_MAKE_ETERNAL
     friend class DeviceManagement;
 
 public:

Kernel/Devices/MemoryDevice.h

@@ -13,7 +13,6 @@
 namespace Kernel {
 
 class MemoryDevice final : public CharacterDevice {
-    AK_MAKE_ETERNAL
     friend class DeviceManagement;
 
 public:

Kernel/Devices/NullDevice.h

@@ -11,7 +11,6 @@
 namespace Kernel {
 
 class NullDevice final : public CharacterDevice {
-    AK_MAKE_ETERNAL
     friend class DeviceManagement;
 
 public:

Kernel/Devices/PCISerialDevice.cpp

@@ -30,7 +30,7 @@ UNMAP_AFTER_INIT void PCISerialDevice::detect()
                 // If this is the first port of the first pci serial device, store it as the debug PCI serial port (TODO: Make this configurable somehow?)
                 if (!is_available())
                     s_the = serial_device;
-                // NOTE: We intentionally leak the reference to serial_device here, as it is eternal
+                // NOTE: We intentionally leak the reference to serial_device here.
             }
 
             dmesgln("PCISerialDevice: Found {} @ {}", board_definition.name, device_identifier.address());

Kernel/Devices/PCISerialDevice.h

@@ -14,7 +14,6 @@
 namespace Kernel {
 
 class PCISerialDevice {
-    AK_MAKE_ETERNAL
 public:
     static void detect();
     static SerialDevice& the();

Kernel/Devices/RandomDevice.h

@@ -11,7 +11,6 @@
 namespace Kernel {
 
 class RandomDevice final : public CharacterDevice {
-    AK_MAKE_ETERNAL
     friend class DeviceManagement;
 
 public:

Kernel/Devices/SerialDevice.h

@@ -12,7 +12,6 @@
 namespace Kernel {
 
 class SerialDevice final : public CharacterDevice {
-    AK_MAKE_ETERNAL
     friend class DeviceManagement;
 
 public:

Kernel/Devices/VMWareBackdoor.h

@@ -39,7 +39,6 @@ struct VMWareCommand {
 };
 
 class VMWareBackdoor {
-    AK_MAKE_ETERNAL;
 
 public:
     VMWareBackdoor();

Kernel/Devices/ZeroDevice.h

@@ -11,7 +11,6 @@
 namespace Kernel {
 
 class ZeroDevice final : public CharacterDevice {
-    AK_MAKE_ETERNAL
     friend class DeviceManagement;
 
 public: