[R] Remove usage of cpp11's `cpp11/altrep.hpp` and `HAS_ALTREP`

[DavisVaughan]

Describe the enhancement requested

cpp11 is moving to require R >=4.0.0 in the next release r-lib/cpp11#411

That means that ALTREP is always available, and the macro HAS_ALTREP is no longer needed, and the file cpp11/altrep.hpp is no longer useful. I'm going to keep them around for a release or two, but if you could remove your reliance on them, then that'd be great!

https://github.com/search?q=repo%3Aapache%2Farrow%20altrep.hpp&type=code

Component(s)

R

[DavisVaughan]

@thisisnic do you think you all would be able to pick this up for the next release?

[thisisnic]

We have a release imminent (the main Arrow C++ one has just happened which means I'm about to start the R package one), and the following release wouldn't be until April, so looks like it makes sense for us to get this into this one - thanks for the heads up!

[thisisnic]

Just saw how long this has been hanging around for, sorry, hope we didn't block you all on anything with this!

[thisisnic]

Issue resolved by pull request 48902
#48902