fix(x64-glibc-217): use modern gcc and python from conda-forge

[underoll]

@vitaliylag made really awesome job in #174 !
I like most of the changes, but building gcc and several versions of python looks a bit overkill.

I'm creating this to show another more straightforward way to get modern gcc and python even on centos:7

My main need is modern nodejs on the legacy el7, so I fixed x64-glibc-217 only.
But it looks like we can use just the same docker image for all centos:7-based recipes.

I assume that modern gcc and python can build old nodejs versions also.
Moreover, we already have them in the repo, so who cares to rebuild them once again.
But if we really want to use different gcc and python versions for previous nodejs builds, we can do that gracefully with conda/mamba:

mamba create -n 'v8.0' gxx=12
mamba create -n 'v14.14' gxx=12 python=3.9
mamba create -n 'v22.3' gxx=15 python=3.13

and then just switch them as

mamba activate 'v22.3'

[rvagg]

I've never heard of mamba, and mamba.pm looks sketchy, so this is going to require some endorsement from others more actively involved here who think this is a good idea. Otherwise, this isn't going to merge, sorry.

[underoll]

mamba.pm looks sketchy

em... looks like mamba.pm is just a hosting for the installer script
https://mamba.readthedocs.io/en/latest/installation/micromamba-installation.html#automatic-install

mamba is a reimplementation of the conda package manager (popular for python, especially for data science) and is part of the conda-forge ecosystem

i changed Miniforge to micromamba in 65211fb
because micromamba looks more suitable for CI