types table: add deprecation warning

lib/types/table.nix

@@ -1,6 +1,13 @@
 { config, options, lib, diskoLib, parent, device, ... }:
 {
-  options = {
+  options = lib.warn ''
+    The legacy table is deprecated and is not recommended to be used anymore.
+    The gpt type is the recommended partition table type.
+    With the legacy table type things like the test framework will not work.
+    if you see errors looking like this:
+      error: The option `disko.devices.disk.disk1.content.partitions."[definition 1-entry 1]".content._config' is read-only, but it's set multiple times.
+    then it's the fault of the legacy table type.
+  '' {
     type = lib.mkOption {
       type = lib.types.enum [ "table" ];
       internal = true;