Auto merge of #15690 - vwvww:issue_14898, r=Wafflespeanut

Add 'use statements with extraneous spaces' tidy check

Add 'use statements with extraneous spaces' tidy check

I added simple check routine for 'use statements with extraneous
spaces' and codes that breaks the check routine in rust_tidy.rs.

* Added a code that using 'use statements with extraneous spaces' code
  in rust_tidy.rs
* Added assertion code in test_tidy.py.
* check_rust function in tidy.py now recognizes the simple case in
  the 'use statements with extraneous spaces'.
* Ran tidy check on rust code and modified a
  code(tests/unit/style/parsing/inherited_text.rs) that is not passing
  on this new tidy check.

TODO: this code has to be refactored to support more general cases, such as tab or newline.

- [X] `./mach build -d` does not report any errors
- [X] ./mach test-tidy does not report any errors
- [X] These changes fix #14898 (github issue number if applicable).
- [X] These changes do not require tests because ./mach test-tidy itself is the test for the code.

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tests/unit/style/parsing/inherited_text.rs

@@ -74,7 +74,7 @@ fn text_emphasis_style_longhand_should_parse_properly() {
 #[test]
 fn test_text_emphasis_position() {
     use style::properties::longhands::text_emphasis_position;
-    use style::properties::longhands::text_emphasis_position::{HorizontalWritingModeValue, VerticalWritingModeValue };
+    use style::properties::longhands::text_emphasis_position::{HorizontalWritingModeValue, VerticalWritingModeValue};
     use style::properties::longhands::text_emphasis_position::SpecifiedValue;
 
     let over_right = parse_longhand!(text_emphasis_position, "over right");