Avoid multiline expression if format specifier is present (#11123)

## Summary

This PR fixes the bug where the formatter would format an f-string and
could potentially change the AST.

For a triple-quoted f-string, the element can't be formatted into
multiline if it has a format specifier because otherwise the newline
would be treated as part of the format specifier.

Given the following f-string:
```python
f"""aaaaaaaaaaaaaaaa bbbbbbbbbbbbbbbbbb ccccccccccc {
    variable:.3f} ddddddddddddddd eeeeeeee"""
```

The formatter sees that the f-string is already multiline so it assumes
that it can contain line breaks i.e., broken into multiple lines. But,
in this specific case we can't format it as:

```python
f"""aaaaaaaaaaaaaaaa bbbbbbbbbbbbbbbbbb ccccccccccc {
    variable:.3f
} ddddddddddddddd eeeeeeee"""
```
                     
Because the format specifier string would become ".3f\n", which is not
the original string (`.3f`).

If the original source code already contained a newline, they'll be
preserved. For example:
```python
f"""aaaaaaaaaaaaaaaa bbbbbbbbbbbbbbbbbb ccccccccccc {
    variable:.3f
} ddddddddddddddd eeeeeeee"""
```

The above will be formatted as:
```py
f"""aaaaaaaaaaaaaaaa bbbbbbbbbbbbbbbbbb ccccccccccc {variable:.3f
} ddddddddddddddd eeeeeeee"""
```

Note that the newline after `.3f` is part of the format specifier which
needs to be preserved.
The Python version is irrelevant in this case.

fixes: #10040 

## Test Plan

Add some test cases to verify this behavior.

crates/ruff_python_formatter/src/context.rs

@@ -1,5 +1,5 @@
 use crate::comments::Comments;
-use crate::other::f_string::FStringContext;
+use crate::other::f_string_element::FStringExpressionElementContext;
 use crate::PyFormatOptions;
 use ruff_formatter::{Buffer, FormatContext, GroupId, IndentWidth, SourceCode};
 use ruff_python_ast::str::Quote;
@@ -128,13 +128,13 @@ impl Debug for PyFormatContext<'_> {
     }
 }
 
-#[derive(Copy, Clone, Debug, Default)]
+#[derive(Clone, Copy, Debug, Default)]
 pub(crate) enum FStringState {
     /// The formatter is inside an f-string expression element i.e., between the
     /// curly brace in `f"foo {x}"`.
     ///
     /// The containing `FStringContext` is the surrounding f-string context.
-    InsideExpressionElement(FStringContext),
+    InsideExpressionElement(FStringExpressionElementContext),
     /// The formatter is outside an f-string.
     #[default]
     Outside,