Improve conda installation instructions

[mefuller]

Motivation or Problem

Writing the documentation to only reference Anaconda is inflexible and bloated as compared with utilizing Miniconda or Conda available in system repositories. This is of particular relevance of storage-limited systems, such as shared high-performance resources where RMG is often installed (which also frequently run RHEL or another Enterpise Linux which includes conda in the repositories, easing administrative burden).

Description of Changes

• Use repositories over Ananconda for proper locations, updates
• switch to Miniconda to reduce download and installation size by 10x
• replace deprecated source with conda in activating environments

Testing

Environments created and RMG-Py, RMG-database installed and tested on Fedora and EL systems

[sevyharris]

This looks good to me. I think it should be ready to go after the two tabs are added so the HTML builds properly.

[JacksonBurns]

Something like this came up in #2437 - the Docker image and CI use miniconda, which does not follow the developer installation instructions. For the same reasons listed in this PR, this should be changed. I am going to resolve the merge conflicts and get this ready to merge, since the same points made are still relevant. @sevyharris could you review after?

[JacksonBurns]

Also adding that almost all of the content that was originally in this PR (like conda activate instead of source activate) has trickled in over time via other PRs.

[mefuller]

So you want me to tidy it up?

[JacksonBurns]

So you want me to tidy it up?

Nope, there was only one conlict, which I resolved. The rest of the changes were already present, so they did not raise conflicts when updating. Thanks for checking in though!

[codecov]

Codecov Report

Merging #2246 (353d769) into main (770a8c8) will not change coverage.
The diff coverage is n/a.

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  Coverage   48.13%   48.13%           
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  Files         110      110           
  Lines       30626    30626           
  Branches     7988     7988           
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  Hits        14743    14743           
  Misses      14353    14353           
  Partials     1530     1530           

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[rwest]

I fixed the issues Sevy noted, and added some more edits.
Looks good to me, but as many of the changes are now mine, we should have someone else review it too.
(fwiw I did build the documentation locally, which for me required some hacks described here, and it rendered OK in HTML)

[JacksonBurns]

LGTM!