Fix #106696: Invalid flag combinations used in #PyObject_GetBuffer

Code using #PyObject_GetBuffer was combining the `PyBUF_FORMAT` and
`PyBUF_SIMPLE` flags, but the documentation specifies that
`PyBUF_FORMAT` can be |'d to any of the flags except `PyBUF_SIMPLE`
because the latter already implies format `B` (unsigned bytes).

The flags in such cases have been replaced with
`PyBUF_ND | PyBUF_FORMAT`, which has the additional requirement that the
buffer must provide it's `shape` field.

This fixes `memoryview` objects raising a `BufferError` when requested,
due to the invalid combination of flags making them be considered
invalid buffers when they would otherwise be valid.

Ref: !106697