Migrate to mason.nvim and setup jdtls

lua/lsp/metals.lua

@@ -42,7 +42,7 @@ return function(on_attach)
     -- NOTE: You may or may not want java included here. You will need it if you
     -- want basic Java support but it may also conflict if you are using
     -- something like nvim-jdtls which also works on a java filetype autocmd.
-    pattern = { "scala", "sbt", "java" },
+    pattern = { "scala", "sbt" },
     callback = function()
       require("metals").initialize_or_attach(metals_config)
     end,