Replace get_c_string_buf_and_size with PyUnicode_AsUTF8AndSize

[WillAyd]

We have a function in pandas/_libs/tslibs/util.pxd called get_c_string_buf_and_size . I think this served a purpose when we had Python 2/3 compat but at the moment it just wraps the standard PyUnicode_AsUTF8AndSize function, so it adds an unnecessary layer

[WillAyd]

On review I don't think this exists in Cython so needs to be added upstream first

[WillAyd]

This will depend on cython/cython#5163

[mmc1718]

take

[WillAyd]

@mmc1718 thanks for offering. We need to wait a bit on this though until our minimum Cython version has this function. This was just added upstream in cython/cython#5163

[mmc1718]

Ah ok, no worries. Thanks for explaining :)

[WillAyd]

The tooling is there now to do this, but looks like it was already solved. Thanks @mmc1718 for your offer