Auto merge of #9295 - Guilherme-Vasconcelos:manual-empty-string-creation, r=dswij

Add `manual_empty_string_creations` lint

Closes #2972

- [x] Followed [lint naming conventions][lint_naming]
- [x] Added passing UI tests (including committed `.stderr` file)
- [x] `cargo test` passes locally
- [x] Executed `cargo dev update_lints`
- [x] Added lint documentation
- [x] Run `cargo dev fmt`

changelog: [`manual_empty_string_creations`]: Add lint for empty String not being created with `String::new()`

clippy_dev/src/new_lint.rs

@@ -155,7 +155,7 @@ fn to_camel_case(name: &str) -> String {
     name.split('_')
         .map(|s| {
             if s.is_empty() {
-                String::from("")
+                String::new()
             } else {
                 [&s[0..1].to_uppercase(), &s[1..]].concat()
             }