Standardize use of Pygments lexers for code block syntax highlighting

[felker]

(work in progress)

A follow up from my comments #646 (comment)

Our mkdocs-material code blocks have enabled the Highlight extension, which uses Pygments for the default syntax highlighter. See https://pygments.org/languages/ for the list of Pygments supported languages/lexers.

Here is a quick survey of the fenced triple-backtick code blocks in our current docs source code

• bash = shell = ...
• python = py = python3 = py3
• output
• yaml
• fortran
• julia
• cmake
• makefile
• C
• C++ = cpp
• markdown = md
• diff

We should be consistent in our application of syntax highlighting, using the correct lexer for all blocks of the same type, etc.

• minor nitpick: authors are starting to use { .bash .no-copy=1 } for example output blocks, but it might be more appropriate to use { .output .no-copy=1 } since the output of a shell command is usually unformatted ASCII, not Bash code

Also we should decide on if/how to use https://pygments.org/docs/terminal-sessions/ lexers throughout our docs, since we are often mixing short examples of code and expected output within a single fenced block, chiefly:

• shell-session = console

• pycon = python-console

For example, this following block in our docs:

```python
>>> import torch
>>> torch.__version__
'2.3.1+cxx11.abi'

Renders as the following, and should be switched to python-console:

Related #621

• Consider changing some of the current loaded extension options, e.g. guess_lang: https://facelessuser.github.io/pymdown-extensions/extensions/highlight/#options
• ./sophia/not_in_nav/data-science/containers/containers.md has multiple uses of ```singularity, but I don't think that is valid.
• ai-testbed/ is the only folder that makes extensive use of ```console, and I havent checked if their usage makes sense
• this needs fixing:

./polaris/applications-and-libraries/applications/vasp.md:154:``` example-script.sh

[felker]

strangely, python-console applied to the above example is categorically worse: