[ruff] Indented form feeds (RUF054) (#16049)

## Summary

Resolves #12321.

The physical-line-based `RUF054` checks for form feed characters that
are preceded by only tabs and spaces, but not any other characters,
including form feeds.

## Test Plan

`cargo nextest run` and `cargo insta test`.

crates/ruff_linter/resources/test/fixtures/ruff/RUF054.py

@@ -0,0 +1,32 @@
+############# Warning ############
+# This file contains form feeds. #
+############# Warning ############
+
+
+# Errors
+
+ 
+
+		
+
+def _():
+		pass
+
+if False:
+    print('F')
+    print('T')
+
+
+# No errors
+
+
+
+
+
+  
+
+def _():
+    pass
+
+def f():
+	pass