refactor: Rename RuleOrigin to Linter

"origin" was accurate since ruff rules are currently always modeled
after one origin (except the Ruff-specific rules).

Since we however want to introduce a many-to-many mapping between codes
and rules, the term "origin" no longer makes much sense. Rules usually
don't have multiple origins but one linter implements a rule first and
then others implement it later (often inspired from another linter).
But we don't actually care much about where a rule originates from when
mapping multiple rule codes to one rule implementation, so renaming
RuleOrigin to Linter is less confusing with the many-to-many system.

ruff_cli/src/commands.rs

@@ -285,7 +285,7 @@ pub fn show_files(
 #[derive(Serialize)]
 struct Explanation<'a> {
     code: &'a str,
-    origin: &'a str,
+    linter: &'a str,
     summary: &'a str,
 }
 
@@ -315,7 +315,7 @@ pub fn explain(rule: &Rule, format: SerializationFormat) -> Result<()> {
                 "{}",
                 serde_json::to_string_pretty(&Explanation {
                     code: rule.code(),
-                    origin: rule.origin().name(),
+                    linter: rule.origin().name(),
                     summary: rule.message_formats()[0],
                 })?
             );

ruff_cli/tests/black_compatibility_test.rs

@@ -13,7 +13,7 @@ use assert_cmd::Command;
 use itertools::Itertools;
 use log::info;
 use ruff::logging::{set_up_logging, LogLevel};
-use ruff::registry::RuleOrigin;
+use ruff::registry::Linter;
 use strum::IntoEnumIterator;
 use walkdir::WalkDir;
 
@@ -175,12 +175,12 @@ fn test_ruff_black_compatibility() -> Result<()> {
         .filter_map(Result::ok)
         .collect();
 
-    let codes = RuleOrigin::iter()
+    let codes = Linter::iter()
         // Exclude ruff codes, specifically RUF100, because it causes differences that are not a
         // problem. Ruff would add a `# noqa: W292`  after the first run, black introduces a
         // newline, and ruff removes the `# noqa: W292` again.
-        .filter(|origin| *origin != RuleOrigin::Ruff)
-        .map(|origin| origin.prefixes().as_list(","))
+        .filter(|linter| *linter != Linter::Ruff)
+        .map(|linter| linter.prefixes().as_list(","))
         .join(",");
     let ruff_args = [
         "-",