Use new base images

[dustinblack]

Changes introduced with this PR

In order to better control drift that can lead to CI build failures, the Dockerfile is updated to use new Arcaflow base images where we can centrally control the OS and core dependencies.

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[dustinblack]

Testable plugin package built by updated CI: quay.io/arcalot/arcaflow-plugin-template-python:new-baseimage_3798fde

[dustinblack]

Dockerfiles for new osbase and buildbase base images are in this repo:
https://github.com/arcalot/arcaflow-plugin-baseimage-python

Base images are in quay here:
arcalotarcaflow-plugin-baseimage-python-osbase
arcalotarcaflow-plugin-baseimage-python-buildbase

Stage 1 of the updated Dockerfile here uses the buildbase image, which inherits the core base OS and python install from the osbase image, installs version-controlled prerequisite python modules, and sets some universal parameters.

Stage 2 of the updated Dockerfile simply uses the osbase image, standardizing the base OS (currently defined in osbase as centos:stream8) and python installs.

[BATMAN-JD]

This is an awesome change that really makes this much cleaner. Well done