Add \IfExplAtLeastTF (see #1004)

[josephwright]

READ ME FIRST: Please understand that in most cases we will not be able to merge a pull request because there are a lot of internal activities needed when updating the LaTeX2e sources. If you have a code suggestion please discuss it with the team first.

Pull requests in this repository are intended for LaTeX Team members only.

Internal housekeeping

Status of pull request

• Feedback wanted
• Under development
• Ready to merge

Checklist of required changes before merge will be approved

• Test file(s) added
• Version and date string updated in changed source files
• Relevant \changes entries in source included
• Relevant changes.txt updated
• ltnewsX.tex (and/or latexchanges.tex) updated

[muzimuzhi]

Some checks failed because tests rolling back to 2022-06-01, 2022-11-01, and 2023-06-01 need to be updated.

l3build save -e pdftex,xetex,luatex \
  tlb-latexrelease-rollback-2022-06-01 \
  tlb-latexrelease-rollback-2022-11-01 \
  tlb-latexrelease-rollback-2023-06-01

[josephwright]

@muzimuzhi Yeah, I was just fixing that

[FrankMittelbach]

maybe not really request changes but suggest changes or think about changes :-)

[FrankMittelbach]

with 2 comments