Debug toolbar crashes xblock api requests with DjangoUnicodeDecodeError

This is on a fresh tutor devstack install - the same environment as #37101

To reproduce:

1. Navigate to the course outline of the demo course in Authoring.
2. Click "New unit".

The page fails with "We encountered a technical error when loading this page. This might be a temporary issue, so please try again in a few minutes. If the problem persists, please go to the Support Page for help."

In the network console, view the following:

Request Method: GET
Request URL: http://studio.local.openedx.io:8001/xblock/container/block-v1:OpenedX+DemoX+DemoCourse+type@vertical+block@0ced03ea1d094e20ad6e18e8daa119fd

(Also observed similar error for:

• http://studio.local.openedx.io:8001/api/contentstore/v1/container_handler/block-v1:OpenedX+DemoX+DemoCourse+type@vertical+block@782386797bfc439d9bcaf187ab4a02d4
• http://studio.local.openedx.io:8001/api/contentstore/v1/container/vertical/block-v1:OpenedX+DemoX+DemoCourse+type@vertical+block@782386797bfc439d9bcaf187ab4a02d4/children
  )

Traceback (most recent call last):
  File "/openedx/venv/lib/python3.11/site-packages/debug_toolbar/store.py", line 22, in default
    return super().default(o)
           ^^^^^^^^^^^^^^^^^^
  File "/openedx/venv/lib/python3.11/site-packages/django/core/serializers/json.py", line 106, in default
    return super().default(o)
           ^^^^^^^^^^^^^^^^^^
  File "/opt/pyenv/versions/3.11.8/lib/python3.11/json/encoder.py", line 180, in default
    raise TypeError(f'Object of type {o.__class__.__name__} '
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

During handling of the above exception (Object of type bytes is not JSON serializable), another exception occurred:
  File "/openedx/venv/lib/python3.11/site-packages/django/utils/encoding.py", line 70, in force_str
    s = str(s, encoding, errors)
        ^^^^^^^^^^^^^^^^^^^^^^^^

During handling of the above exception ('utf-8' codec can't decode byte 0xbc in position 2: invalid start byte), another exception occurred:
  File "/openedx/venv/lib/python3.11/site-packages/django/core/handlers/exception.py", line 55, in inner
    response = get_response(request)
               ^^^^^^^^^^^^^^^^^^^^^
  File "/openedx/venv/lib/python3.11/site-packages/debug_toolbar/middleware.py", line 145, in __call__
    return self._postprocess(request, response, toolbar)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/openedx/venv/lib/python3.11/site-packages/debug_toolbar/middleware.py", line 182, in _postprocess
    panel.generate_stats(request, response)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/openedx/venv/lib/python3.11/site-packages/debug_toolbar/panels/cache.py", line 212, in generate_stats
    self.record_stats(
    ^
  File "/openedx/venv/lib/python3.11/site-packages/debug_toolbar/panels/__init__.py", line 194, in record_stats
    self.toolbar.store.save_panel(
    ^
  File "/openedx/venv/lib/python3.11/site-packages/debug_toolbar/store.py", line 122, in save_panel
    cls._request_store[request_id][panel_id] = serialize(data)
                                               ^^^^^^^^^^^^^^^
  File "/openedx/venv/lib/python3.11/site-packages/debug_toolbar/store.py", line 32, in serialize
    return json.dumps(data, cls=DebugToolbarJSONEncoder)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/pyenv/versions/3.11.8/lib/python3.11/json/__init__.py", line 238, in dumps
    **kw).encode(obj)
          ^^^^^^^^^^^
  File "/opt/pyenv/versions/3.11.8/lib/python3.11/json/encoder.py", line 200, in encode
    chunks = self.iterencode(o, _one_shot=True)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/pyenv/versions/3.11.8/lib/python3.11/json/encoder.py", line 258, in iterencode
    return _iterencode(o, 0)
           ^^^^^^^^^^^^^^^^^
  File "/openedx/venv/lib/python3.11/site-packages/debug_toolbar/store.py", line 25, in default
    return force_str(o)
           ^^^^^^^^^^^^
  File "/openedx/venv/lib/python3.11/site-packages/django/utils/encoding.py", line 74, in force_str
    raise DjangoUnicodeDecodeError(s, *e.args)
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Exception Type: DjangoUnicodeDecodeError at /xblock/container/block-v1:OpenedX+DemoX+DemoCourse+type@vertical+block@0ced03ea1d094e20ad6e18e8daa119fd
Exception Value: 'utf-8' codec can't decode byte 0xbc in position 2: invalid start byte. You passed in b'x\x01\xbc\xbd\t\xa0\x1c\xd7U&,\xdb\xda\xfc$k\xf1*\'\xc4\xa9\x18/r\xac\'\xd5\xbe(\xb6cY\xb2-\xd9\x96-KJ\xe2Lb:\xb7\xea\xdez\xddV\xbf\xee\x97^$\xbd,\x8c3@p2\r\x93\x81GH\x02$\x01~\x06\x03\x13\x08K \xc0\xf0\x93aK\x80\x0c\x18\xc8\x9f1\xbb\t\xcb\x98-\x98-1\x84\x90\xff\xbbu\xbb\xba\xef{\xdd\xa5{\xab_i\x12\xc7\x91\xde;Uu\xeb\xbb\xa7\xce=\xe7\xdes\xbe\xf3\xe4\xc6o\xdb\xb0\xe1\x92\r\xfc?o_\xd9;\xb8\xac\xd6\xa0+\x83+\xe2n\xbb\xb5\xbf\x1d?\xc1\x92\x1e\xff\xfb\xd6G\xb2?\x1e\xa3+\xdf\xbar\xdb;V\x0eo\xaf\x0f\xae;\xf9M\xbf\xf1\xcd7}\xe5\x9d7\xfc\xd4J<\xd8\xd8i\xb7{+\x83\xdd\xe7\x17\xdb\xb4\xdfd\xfb\xfb\xbdFs\xff\x19\xb6\xdc\xc5\xa5\xf74\xdb\xc9\x99\x07\xd92.\x1dlN\xda\xfdN\x97\x8d\xff\xf0\xce\x95w\xac\x0cv-u\xd8\xd9F\xbb\xdf\xad\x9de\x9dn\xa3\xddZ\xa9o\x1c>\xe5J\xcb}\xff-\xb7\xdf\x7f\xfd\'\xaf\xc2Sv\xb5;\x8d\x85F\x8b4/  ...[clipped]' (<class 'bytes'>)

The large bytestring is zlib compressed data.
The extracted data appears to be a kind of memory dump of the course outline(?):

D@@A@@@@@}(C_idMbson.objectidObjectId)CLhWRΎ$^bDrootQxmodule.util.keysBlockKeyFcourseFcoursePprevious_versionhD)CLhR14&+GYSbPoriginal_versionhD)CLhR14&+GYMb    edited_byKD     edited_ondatetimedatetimeC
GAAX"MLbson.tz_utilKFixedOffsethW       timedeltaK@K@K@RCUTCR}(T_FixedOffset__offseth!R_FixedOffset__nameh"ubRFblocks}(h

...

A@@JjKA@@NjLA@@NjMA@@NjNA@@Nububh
Gproblem ef8c3814d2ce47c6927a8310bba4b849h2)}(h5h6}(Ldisplay_name'Multiple Choice with Hints and FeedbackmarkdownXQC@@<p><img style="width: 100%;" src="/static/Abacus.png" alt="An abacus with two beads pushed up in the last column, 1 bead in the 2nd to last, and one bead pushed down on the top right. " /></p>
>>In the traditional abacus shown above, what number is represented?<<

( ) 3


...

Start by reproducing the failure through the Authoring course outline and read the traceback paths in debug_toolbar/store.py and debug_toolbar/panels/cache.py. Confirm the failing request data is compressed bytes, then verify that the XBlock and contentstore requests complete without the debug toolbar raising DjangoUnicodeDecodeError.