Insert empty line between suite and alternative branch after def/class (#12294)

When there is a function or class definition at the end of a suite
followed by the beginning of an alternative block, we have to insert a
single empty line between them.

In the if-else-statement example below, we insert an empty line after
the `foo` in the if-block, but none after the else-block `foo`, since in
the latter case the enclosing suite already adds empty lines.

```python
if sys.version_info >= (3, 10):
    def foo():
        return "new"
else:
    def foo():
        return "old"
class Bar:
    pass
```

To do so, we track whether the current suite is the last one in the
current statement with a new option on the suite kind.

Fixes #12199

---------

Co-authored-by: Micha Reiser <micha@reiser.io>

crates/ruff_python_formatter/resources/test/fixtures/ruff/newlines.py

@@ -249,6 +249,68 @@ if True:
     print()
 
 
+if True:
+    def a():
+        return 1
+else:
+    pass
+
+if True:
+    # fmt: off
+    def a():
+        return 1
+    # fmt: on
+else:
+    pass
+
+match True:
+    case 1:
+        def a():
+            return 1
+    case 1:
+        def a():
+            return 1
+
+try:
+    def a():
+        return 1
+except RuntimeError:
+    def a():
+        return 1
+
+try:
+    def a():
+        return 1
+finally:
+    def a():
+        return 1
+
+try:
+    def a():
+        return 1
+except RuntimeError:
+    def a():
+        return 1
+except ZeroDivisionError:
+    def a():
+        return 1
+else:
+    def a():
+        return 1
+finally:
+    def a():
+        return 1
+
+if raw:
+    def show_file(lines):
+        for line in lines:
+            pass
+            # Trailing comment not on function or class
+
+else:
+    pass
+
+
 # NOTE: Please keep this the last block in this file. This tests that we don't insert
 # empty line(s) at the end of the file due to nested function
 if True:

crates/ruff_python_formatter/resources/test/fixtures/ruff/newlines.pyi

@@ -154,8 +154,14 @@ def f():
     pass
 
 
+if True:
+    def a():
+        return 1
+else:
+    pass
 
 
 # comment
 
 x = 1
+