feat: add witnesses for function_const_removed (#977)

* feat: add const witnesses

* Apply suggestions from code review

---------

Co-authored-by: Predrag Gruevski <2348618+obi1kenobi@users.noreply.github.com>

src/lints/function_const_removed.ron

@@ -48,4 +48,9 @@ SemverQuery(
     },
     error_message: "A publicly-visible function is no longer `const` and can no longer be used in a `const` context.",
     per_result_error_template: Some("function {{join \"::\" path}} in file {{span_filename}}:{{span_begin_line}}"),
+    witness: (
+        hint_template: r#"const fn witness() {
+    {{join "::" path}}(...);
+}"#,
+    ),
 )

test_outputs/witnesses/function_const_removed.snap

@@ -0,0 +1,12 @@
+---
+source: src/query.rs
+description: "Lint `function_const_removed` did not have the expected witness output.\nSee https://github.com/obi1kenobi/cargo-semver-checks/blob/main/CONTRIBUTING.md#testing-witnesses\nfor more information."
+expression: "&actual_witnesses"
+---
+[["./test_crates/function_const_removed/"]]
+filename = 'src/lib.rs'
+begin_line = 1
+hint = '''
+const fn witness() {
+    function_const_removed::add(...);
+}'''