chore(libalgo: avl): add GDB pretty printer for avl_t

This is a nice and easy to have feature to help us eventual issues with
our AVL implementation. It should not be useful anymore once we've
debugged our implementation, but I'll leave it anyway just in case.

.gdbinit

@@ -0,0 +1 @@
+source scripts/gdb/pretty_printer.py

scripts/debug.sh

@@ -33,6 +33,7 @@ gdb --symbol ./build/kernel/kernel.sym \
     -iex "set pagination of" \
     -iex "target remote localhost:1234" \
     "${BREAKPOINTS[@]}" \
+    -x "${GITROOT}/.gdbinit" \
     -ex "continue"
 
 echo "[INFO] Terminating debugging session"

scripts/gdb/pretty_printer.py

@@ -0,0 +1,40 @@
+class Avl:
+
+    def __init__(self, val) -> None:
+        self.address = val.address
+        self.height = val["height"]
+        self.parent = val["parent"]
+        self.left = val["left"]
+        self.right = val["right"]
+
+    def to_string_rec(self, parent, depth) -> str:
+        prefix = '  ' * depth
+        string = f'''{self.address} {{
+  {prefix}height: {self.height}
+  {prefix}parent: {self.parent}{"" if self.parent == parent else " (error)"}
+'''
+
+        if self.left:
+            string += f"  {prefix}left@{Avl(self.left.dereference()).to_string_rec(self.address, depth + 1)}\n"
+        if self.right:
+            string += f"  {prefix}right@{Avl(self.right.dereference()).to_string_rec(self.address, depth + 1)}\n"
+
+        string += f'{prefix}}}'
+        return string
+
+    def to_string(self):
+        return f"avl@{self.to_string_rec(0, 0)}"
+
+
+def pretty_printers(val):
+    printers = {
+            "avl_t": Avl
+    }
+
+    if str(val.type) in printers:
+        return printers[str(val.type)](val)
+
+    return None
+
+
+gdb.pretty_printers.append(pretty_printers)