require("internet").request now returns a function object

The function object can be called to read from the stream, same usage as before
But the object also exposes the request handle userdata, to allow calling close for example:

```
local request = require("internet").request("http://www.google.com")
print(request()) -- same as before
request:close() -- clean up resources now, as opposed to waiting for gc
```

closes #2255

src/main/resources/assets/opencomputers/loot/openos/lib/internet.lua

@@ -11,10 +11,10 @@ function internet.request(url, data, headers)
   checkArg(2, data, "string", "table", "nil")
   checkArg(3, headers, "table", "nil")
 
-  local inet = component.internet
-  if not inet then
+  if not component.isAvailable("internet") then
     error("no primary internet card found", 2)
   end
+  local inet = component.internet
 
   local post
   if type(data) == "string" then
@@ -31,23 +31,35 @@ function internet.request(url, data, headers)
     error(reason, 2)
   end
 
-  return function()
-    while true do
-      local data, reason = request.read()
-      if not data then
-        request.close()
-        if reason then
-          error(reason, 2)
-        else
-          return nil -- eof
+  return setmetatable(
+  {
+    ["()"] = "function():string -- Tries to read data from the socket stream and return the read byte array.",
+    close = setmetatable({},
+    {
+      __call = request.close,
+      __tostring = function() return "function() -- closes the connection" end
+    })
+  },
+  {
+    __call = function()
+      while true do
+        local data, reason = request.read()
+        if not data then
+          request.close()
+          if reason then
+            error(reason, 2)
+          else
+            return nil -- eof
+          end
+        elseif #data > 0 then
+          return data
         end
-      elseif #data > 0 then
-        return data
+        -- else: no data, block
+        os.sleep(0)
       end
-      -- else: no data, block
-      os.sleep(0)
-    end
-  end
+    end,
+    __index = request,
+  })
 end
 
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