Consistently name comment own line/end-of-line line_position() (#5215)

## Summary

Previously, `DecoratedComment` used `text_position()` and
`SourceComment` used `position()`. This PR unifies this to
`line_position` everywhere.

## Test Plan

This is a rename refactoring.

crates/ruff_python_formatter/src/statement/stmt_while.rs

@@ -44,7 +44,7 @@ impl FormatNodeRule<StmtWhile> for FormatStmtWhile {
             // Split between leading comments before the `else` keyword and end of line comments at the end of
             // the `else:` line.
             let trailing_start =
-                or_else_comments.partition_point(|comment| comment.position().is_own_line());
+                or_else_comments.partition_point(|comment| comment.line_position().is_own_line());
             let (leading, trailing) = or_else_comments.split_at(trailing_start);
 
             write!(