Refactor internals of @__VERSION__

Based upon suggestions here:
JuliaLang/Pkg.jl#1501

src/version.jl

@@ -1,5 +1,15 @@
 # TODO: Temporary until this is turned into a package
-using Pkg
+using Pkg: Pkg
+
+# https://github.com/JuliaLang/julia/pull/33128
+if VERSION < v"1.4.0-DEV.397"
+    function pkgdir(m::Module)
+        rootmodule = Base.moduleroot(m)
+        path = pathof(rootmodule)
+        path === nothing && return nothing
+        return dirname(dirname(path))
+    end
+end
 
 """
     @__VERSION__ -> Union{VersionNumber, Nothing}
@@ -8,31 +18,12 @@ Get the `VersionNumber` of the package which expands this macro. If executed out
 package `nothing` will be returned.
 """
 macro __VERSION__()
-    ctxt = Pkg.Types.Context()
-    pkg_id = Base.PkgId(__module__)
-    pkg_id.uuid === nothing && return nothing
-
-    project = ctxt.env.project
-    project_name = @static if v"1.0-" <= VERSION < v"1.1-"
-        project["name"]
-    else
-        project.name
-    end
+    pkg_dir = pkgdir(__module__)
 
-    pkg_info = if project_name == pkg_id.name
-        project
+    if pkg_dir !== nothing
+        project_data = Pkg.TOML.parsefile(Pkg.Types.projectfile_path(pkg_dir))
+        return VersionNumber(project_data["version"])
     else
-        _ctxt = @static VERSION < v"1.4-" ? ctxt.env : ctxt
-        Pkg.Types.manifest_info(_ctxt, pkg_id.uuid)
+        return nothing
     end
-
-    version = @static if v"1.0-" <= VERSION < v"1.1-"
-        VersionNumber(pkg_info["version"])
-    elseif v"1.1-" <= VERSION < v"1.2-"
-        VersionNumber(pkg_info.version)
-    else
-        pkg_info.version
-    end
-
-    return version
 end