AASTeX v7 feature: adopt core LaTeX tagged PDF capabilities

[augustfly]

As of 2023-06-01 LaTeX released core upgrades to create tagged (for accessibility) PDFs via pdflatex and xelatex. See https://www.latex-project.org/news/2023/06/10/issue37-of-latex2e-released/

This functionality must be considered for aastex 7