We seem to be wasting a lot of internal memory on random mallocs(),
preventing us from late-initializing bluetooth/BLE.

Fixes #13 . Maybe. We'll see with time.

I think a more complete approach would be to force all micropython
allocations to land in SPIRAM? Or maybe use some memory watermarking to
make the micropython allocator only use internal memory if there's
plenty of it available, enough to initialize BLE?