Add a Lua build-system (#28854)

Reworking lua to allow easier substitution of the base lua implementation.

Also adding in a maintained version of luajit and re-factoring the entire stack 
to use a custom build-system to centralize functionality like environment 
variable management and luarocks installation.

The `lua-lang` virtual is now versioned so that a package that requires 
Lua 5.1 semantics can get any lua, but one that requires 5.2 will only 
get upstream lua.

The luaposix package requires lua-bit32, but only when built with a 
lua conforming to version 5.1.  This adds the package, and the 
dependencies, but exposed a problem with luarocks dependency 
detection.  Since we're  installing each package in its own "tree" and 
there's no environment  variable to list extra trees, spack now 
generates a luarocks config  file that lists all the trees of all the 
dependencies, and references  it by setting `LUAROCKS_CONFIG` 
in the build environment of every LuaPackage.  This allows luarocks 
to find the spack installed  dependencies correctly rather than 
trying (and failing) to download them.

Co-authored-by: Adam J. Stewart <ajstewart426@gmail.com>
Co-authored-by: Tom Scogland <tscogland@llnl.gov>
Co-authored-by: Massimiliano Culpo <massimiliano.culpo@gmail.com>

etc/spack/defaults/packages.yaml

@@ -35,7 +35,8 @@ packages:
       jpeg: [libjpeg-turbo, libjpeg]
       lapack: [openblas, amdlibflame]
       libllvm: [llvm, llvm-amdgpu]
-      lua-lang: [lua, lua-luajit]
+      lua-lang: [lua, lua-luajit-openresty, lua-luajit]
+      luajit: [lua-luajit-openresty, lua-luajit]
       mariadb-client: [mariadb-c-client, mariadb]
       mkl: [intel-mkl]
       mpe: [mpe2]