Deprecate py27 (linux), add py39 (osx)

[timkpaine]

Fixes #1334, adds py39 now that brew defaults this on OSX.

[timkpaine]

builds all passing except the 2 that require docker changes, so looks good

[sc1f]

Looks good - will need a rebuild of the Docker images, and a full tagged build run to check if the wheel builds work.

[texodus]

The Dockerfile modifications in this file do not build - it appears as if the method on step 42 for acquiring nodejs via yum has bit-rotted, which I recognize was not touched by this PR, but nonetheless ...

The experience of discovering this after >1hr of docker build, suggests strongly to me we need a better method of building Python, perhaps we build these images exclusively from Azure? Are these images needed still now that the pyarrow dependency has been removed?

Regardless, two things are true, (1) I cannot merge this PR until the Dockerfile builds, and (2) addressing this tech debt must pre-empt any future image dists.

[timkpaine]

I've updated and tested building the docker images from scratch. They are necessary as azure does not provide a manylinux compatible environment, so in order to dist linux wheels we need these docker images.

[timkpaine]

(I've also dropped python2 in these last changes)

[texodus]

(I've also dropped python2 in these last changes)

Nice try - I've refactored these changes to #1374

[texodus]

Upon further review, the pypa/manylinux2010_x86_64 container we relied upon is now non-reproducible, as the upper-bound of python2 compatible versions is above the lower-bound of CentOS 6 compatible versions. This makes python2 effectively deprecated, even if this image was preserved.

Which means that 0.6.2 is the last python2 "compatible" version that will be published - insofar as perspective-python can be compatible with a language whose own support has been deprecated.