Load l3keys2e only if required

[josephwright]

Current release lipsum avoids force-loading xparse by checking for \NewDocumentCommand, but does not do the same for l3keys2e. Switching to using \ProcessKeyOptions if available would cut out a dependency.

[josephwright]

Something like

\IfFormatAtLeastTF{2022-06-01}
  {\ProcessKeyOptions[lipsum]}
  {
    \RequirePackage{l3keys2e}
    \ProcessKeysOptions{lipsum}
  }

in place of current lines

\RequirePackage{l3keys2e}
...
\ProcessKeysOptions{lipsum}

is all that's needed.