mypystubs: add kernel

python_payload/mypystubs/kernel.pyi

+class task:
+    """Not exposed in the API, used by scheduler_snapshot"""
+
+    #: Name of the task
+    name: str
+
+    #: One of RUNNING, READY, BLOCKED, SUSPENDED, DELETED, INVALID
+    state: int
+
+    #: man i don't even know
+    number: int
+
+    #: you get the idea
+    stack_left: int
+    run_time: int
+    core_affinity: int
+
+class scheduler_snapshot:
+    total_runtime: int
+    tasks: list[task]
+
+class heap_kind_stats:
+    """Not exposed in the API, used by heap_stats"""
+
+    total_free_bytes: int
+    total_allocated_bytes: int
+    largest_free_block: int
+
+class heap_stats:
+    general: heap_kind_stats
+    dma: heap_kind_stats
+
+RUNNING: int
+READY: int
+BLOCKED: int
+SUSPENDED: int
+DELETED: int
+INVALID: int