Formatter: Run generate.py for ElifElseClauses (#5864)

**Summary** This removes the diff for the next user of `generate.py`.
It's effectively a refactoring.

**Test Plan** No functional changes

crates/ruff_python_formatter/src/other/elif_else_clause.rs

@@ -0,0 +1,16 @@
+use crate::statement::stmt_if::format_elif_else_clause;
+use crate::{FormatNodeRule, PyFormatter};
+use ruff_formatter::FormatResult;
+use rustpython_parser::ast::ElifElseClause;
+
+/// Note that this implementation misses the leading newlines before the leading comments because
+/// it does not have access to the last node of the previous branch. The `StmtIf` therefore doesn't
+/// call this but `format_elif_else_clause` directly.
+#[derive(Default)]
+pub struct FormatElifElseClause;
+
+impl FormatNodeRule<ElifElseClause> for FormatElifElseClause {
+    fn fmt_fields(&self, item: &ElifElseClause, f: &mut PyFormatter) -> FormatResult<()> {
+        format_elif_else_clause(item, f, None)
+    }
+}

crates/ruff_python_formatter/src/other/mod.rs

@@ -4,6 +4,7 @@ pub(crate) mod arg_with_default;
 pub(crate) mod arguments;
 pub(crate) mod comprehension;
 pub(crate) mod decorator;
+pub(crate) mod elif_else_clause;
 pub(crate) mod except_handler_except_handler;
 pub(crate) mod identifier;
 pub(crate) mod keyword;