[tools] Commit memory debug (et al) tooling

These are some changes I made to debug tooling while tracking down the
bugfix in the previous commit.

Each `scripts/debug_*_alloc.gdb` script has gdb output a `*_allocs.txt`
file, which in turn can be parsed by the `scripts/parse_*_allocs.py`
script to find errors.

scripts/parse_heap_allocs.py

@@ -0,0 +1,62 @@
+#!/usr/bin/env python3
+
+from bisect import bisect_left, insort
+from operator import attrgetter
+
+by_start = attrgetter('start')
+
+class alloc:
+    def __init__(self, start, size):
+        self.start = start
+        self.size = size
+
+    @property
+    def end(self):
+        return self.start + self.size
+
+    def overlaps(self, other):
+        return other.start < self.end and other.end > self.start
+
+    def __str__(self):
+        return f"[{self.start:012x} - {self.end:012x}]"
+
+    def __gt__(self, other):
+        return self.start > other.start
+
+def add_alloc(allocs, addr, length):
+    a = alloc(addr, length)
+    for existing in allocs:
+        if a.overlaps(existing):
+            print(f"ERROR: allocation {a} overlaps existing {existing}")
+    insort(allocs, a)
+
+def remove_alloc(allocs, addr):
+    a = alloc(addr, 0)
+    i = bisect_left(allocs, a)
+    if len(allocs) > i and allocs[i].start == addr:
+        del allocs[i]
+    else:
+        print(f"ERROR: freeing unallocated {a}")
+
+def parse_line(allocs, line):
+    args = line.strip().split()
+    match args:
+        case ['+', addr, length]:
+            add_alloc(allocs, int(addr, base=16), int(length))
+        case ['-', addr]:
+            remove_alloc(allocs, int(addr, base=16))
+        case _:
+            pass
+
+def parse_file(f):
+    allocs = []
+    for line in f.readlines():
+        parse_line(allocs, line)
+
+if __name__ == "__main__":
+    import sys
+    if len(sys.argv) > 1:
+        with open(sys.argv[1]) as f:
+            parse_file(f)
+    else:
+        parse_file(sys.stdin)