Placement refactor (#6034)

## Summary

This PR is a refactoring of placement.rs. The code got more consistent,
some comments were updated and some dead code was removed or replaced
with debug assertions. It also contains a bugfix for the placement of
end-of-branch comments with nested bodies inside try statements that
occurred when refactoring the nested body loop.

## Test Plan

The existing test cases don't change. I added a couple of cases that i
think should be tested but weren't, and a regression test for the bugfix

crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/attribute.py

@@ -101,3 +101,9 @@ x53 = (
     a.askjdfahdlskjflsajfadhsaf.akjdsf.aksjdlfadhaljsashdfljaf.askjdflhasfdlashdlfaskjfd.asdkjfksahdfkjafs
 )
 
+x6 = (
+    # Check assumption with enclosing nodes
+    a.b
+)
+
+

crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/starred.py

@@ -2,14 +2,14 @@ call(
     # Leading starred comment
     * # Trailing star comment
     [
-        # Leading value commnt
+        # Leading value comment
         [What, i, this, s, very, long, aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa]
     ] # trailing value comment
 )
 
 call(
     # Leading starred comment
-    * ( # Leading value commnt
+    * ( # Leading value comment
         [What, i, this, s, very, long, aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa]
     ) # trailing value comment
 )

crates/ruff_python_formatter/resources/test/fixtures/ruff/statement/if.py

@@ -86,3 +86,16 @@ def f():
         pass
 
         # comment
+
+if True:
+    def f2():
+        pass
+        # 1
+else:
+    def f2():
+        pass
+        # 2
+
+if True: print("a") # 1
+elif True: print("b") # 2
+else: print("c") # 3

crates/ruff_python_formatter/resources/test/fixtures/ruff/statement/try.py

@@ -99,3 +99,23 @@ try:
         print(1)  # issue7208
 except A:
     pass
+
+try:
+    f()  # end-of-line last comment
+except RuntimeError:
+    raise
+
+try:
+    def f2():
+        pass
+        # a
+except:
+    def f2():
+        pass
+        # b
+
+try: pass # a
+except ZeroDivisionError: pass # b
+except: pass # b
+else: pass # d
+finally: pass # c