add irep and lua-lang virtual dependency (#22492)

This adds a package for `irep`, a tool for reading `lua` input decks from 
Fortran, C, and C++.

`irep` can be built with either `lua` or `luajit`.  To address this, we also add
a virtual package for lua called `lua-lang`.  `luajit` isn't, by default, a drop-in
replacement for `lua`, but we add a `+lualinks` variant to it that adds symlinks
that make it behave like `lua@5.1`.  With this variant enabled, it provides the
`lua-lang` virtual.  `lua` always provides `lua-lang`.

- [x] add `irep` package
- [x] add `+lualinks` variant to `lua-luajit`
- [x] create `lua-lang` virtual, provided by `lua` and `luajit+lualinks`

Co-authored-by: Kayla Richarda Butler <butler59@quartz1148.llnl.gov>
Co-authored-by: Todd Gamblin <tgamblin@llnl.gov>

etc/spack/defaults/packages.yaml

@@ -34,6 +34,7 @@ packages:
       java: [openjdk, jdk, ibm-java]
       jpeg: [libjpeg-turbo, libjpeg]
       lapack: [openblas, amdlibflame]
+      lua-lang: [lua, lua-luajit]
       mariadb-client: [mariadb-c-client, mariadb]
       mkl: [intel-mkl]
       mpe: [mpe2]