imports_granularity=Item

Summary: [Post about this change](https://fb.workplace.com/groups/rust.language/posts/8804682282913642)

Reviewed By: zertosh

Differential Revision: D37459034

fbshipit-source-id: d9b29a4ac5749aaf48322a148ba317f052fe7c6e

rustfmt.toml

@@ -1,6 +1,7 @@
 # Get help on options with `rustfmt --help=config`
 # Please keep these in alphabetical order.
 edition = "2021"
+imports_granularity = "Item"
 merge_derives = false
 use_field_init_shorthand = true
 version = "Two"