gh-36436: src/sage/misc/latex.py: replace tmp_dir()
These bits of code only use one temporary file, but they call a function
`_run_latex_()` that writes its output file to the same directory as its
input file. Since we don't want the output path to be predictable (for
security reasons), we have to "hide" the one temporary file inside of a
temporary directory that will only be writable by the Sage user.
In other words: standard `tempfile.TemporaryDirecrory()` replacement.
Issue: https://github.com/sagemath/sage/issues/36322
URL: https://github.com/sagemath/sage/pull/36436
Reported by: Michael Orlitzky
Reviewer(s): Marc Mezzarobba
