Report use statements that use {} with only one entry

[jdm]

Our desired code style is:

use something::foo::Bar;

not

use something::foo::{Bar};

Let's report these lines automatically as part of test-tidy.

Code: python/tidy/servo_tidy/tidy.py
Test: Add one to test_rust in python/tidy/servo_tidy_tests/test_tidy.py, which checks python/tidy/servo_tidy_tests/rust_tidy.rs. Run with ./mach test-tidy --self.

[mbrubeck]

There's no longer any natural way to format a list of imports from the same module, where just one of the imports needs to wrap to the next line:

// ERROR: use statement contains braces for single import
use script_layout_interface::restyle_damage::{BUBBLE_ISIZES, REFLOW, REFLOW_OUT_OF_FLOW};
use script_layout_interface::restyle_damage::{RESOLVE_GENERATED_CONTENT};

// ERROR: use statement is not in alphabetical order
use script_layout_interface::restyle_damage::{BUBBLE_ISIZES, REFLOW, REFLOW_OUT_OF_FLOW};
use script_layout_interface::restyle_damage::RESOLVE_GENERATED_CONTENT;

Could we either revert this change, or change the alphabetization rule to ignore braces?

[jdm]

Ignoring braces will require reformatting the whole tree. Reverting this change will be less work.