fix(builtins): handle buf's lack of stdin support

See this issue for info: bufbuild/buf#1035
For formatting, the fix is to write to and read from a temp file.
Diagnostics require project context, which a temp file can't provide, so
the diagnostics source now runs only on save.

lua/null-ls/builtins/diagnostics/buf.lua

@@ -1,15 +1,15 @@
 local h = require("null-ls.helpers")
 local methods = require("null-ls.methods")
 
-local DIAGNOSTICS = methods.internal.DIAGNOSTICS
+local DIAGNOSTICS_ON_SAVE = methods.internal.DIAGNOSTICS_ON_SAVE
 
 return h.make_builtin({
     name = "buf_lint",
     meta = {
         url = "https://github.com/bufbuild/buf",
         description = "A new way of working with Protocol Buffers.",
     },
-    method = DIAGNOSTICS,
+    method = DIAGNOSTICS_ON_SAVE,
     filetypes = { "proto" },
     generator_opts = {
         command = "buf",

lua/null-ls/builtins/formatting/buf.lua

@@ -10,14 +10,16 @@ return h.make_builtin({
         description = "A new way of working with Protocol Buffers.",
     },
     method = FORMATTING,
+    to_temp_file = true,
+    from_temp_file = true,
     filetypes = { "proto" },
     generator_opts = {
         command = "buf",
         args = {
             "format",
+            "-w",
             "$FILENAME",
         },
-        to_stdin = true,
     },
     factory = h.formatter_factory,
 })