New AST nodes for f-string elements (#8835)

Rebase of #6365 authored by @davidszotten.

## Summary

This PR updates the AST structure for an f-string elements.

The main **motivation** behind this change is to have a dedicated node
for the string part of an f-string. Previously, the existing
`ExprStringLiteral` node was used for this purpose which isn't exactly
correct. The `ExprStringLiteral` node should include the quotes as well
in the range but the f-string literal element doesn't include the quote
as it's a specific part within an f-string. For example,

```python
f"foo {x}"
# ^^^^
# This is the literal part of an f-string
```

The introduction of `FStringElement` enum is helpful which represent
either the literal part or the expression part of an f-string.

### Rule Updates

This means that there'll be two nodes representing a string depending on
the context. One for a normal string literal while the other is a string
literal within an f-string. The AST checker is updated to accommodate
this change. The rules which work on string literal are updated to check
on the literal part of f-string as well.

#### Notes

1. The `Expr::is_literal_expr` method would check for
`ExprStringLiteral` and return true if so. But now that we don't
represent the literal part of an f-string using that node, this improves
the method's behavior and confines to the actual expression. We do have
the `FStringElement::is_literal` method.
2. We avoid checking if we're in a f-string context before adding to
`string_type_definitions` because the f-string literal is now a
dedicated node and not part of `Expr`.
3. Annotations cannot use f-string so we avoid changing any rules which
work on annotation and checks for `ExprStringLiteral`.

## Test Plan

- All references of `Expr::StringLiteral` were checked to see if any of
the rules require updating to account for the f-string literal element
node.
- New test cases are added for rules which check against the literal
part of an f-string.
- Check the ecosystem results and ensure it remains unchanged.

## Performance

There's a performance penalty in the parser. The reason for this remains
unknown as it seems that the generated assembly code is now different
for the `__reduce154` function. The reduce function body is just popping
the `ParenthesizedExpr` on top of the stack and pushing it with the new
location.

- The size of `FStringElement` enum is the same as `Expr` which is what
it replaces in `FString::format_spec`
- The size of `FStringExpressionElement` is the same as
`ExprFormattedValue` which is what it replaces

I tried reducing the `Expr` enum from 80 bytes to 72 bytes but it hardly
resulted in any performance gain. The difference can be seen here:
- Original profile: https://share.firefox.dev/3Taa7ES
- Profile after boxing some node fields:
https://share.firefox.dev/3GsNXpD

### Backtracking

I tried backtracking the changes to see if any of the isolated change
produced this regression. The problem here is that the overall change is
so small that there's only a single checkpoint where I can backtrack and
that checkpoint results in the same regression. This checkpoint is to
revert using `Expr` to the `FString::format_spec` field. After this
point, the change would revert back to the original implementation.

## Review process

The review process is similar to #7927. The first set of commits update
the node structure, parser, and related AST files. Then, further commits
update the linter and formatter part to account for the AST change.

---------

Co-authored-by: David Szotten <davidszotten@gmail.com>

crates/ruff_python_formatter/src/generated.rs

@@ -1534,42 +1534,6 @@ impl<'ast> IntoFormat<PyFormatContext<'ast>> for ast::ExprCall {
     }
 }
 
-impl FormatRule<ast::ExprFormattedValue, PyFormatContext<'_>>
-    for crate::expression::expr_formatted_value::FormatExprFormattedValue
-{
-    #[inline]
-    fn fmt(&self, node: &ast::ExprFormattedValue, f: &mut PyFormatter) -> FormatResult<()> {
-        FormatNodeRule::<ast::ExprFormattedValue>::fmt(self, node, f)
-    }
-}
-impl<'ast> AsFormat<PyFormatContext<'ast>> for ast::ExprFormattedValue {
-    type Format<'a> = FormatRefWithRule<
-        'a,
-        ast::ExprFormattedValue,
-        crate::expression::expr_formatted_value::FormatExprFormattedValue,
-        PyFormatContext<'ast>,
-    >;
-    fn format(&self) -> Self::Format<'_> {
-        FormatRefWithRule::new(
-            self,
-            crate::expression::expr_formatted_value::FormatExprFormattedValue::default(),
-        )
-    }
-}
-impl<'ast> IntoFormat<PyFormatContext<'ast>> for ast::ExprFormattedValue {
-    type Format = FormatOwnedWithRule<
-        ast::ExprFormattedValue,
-        crate::expression::expr_formatted_value::FormatExprFormattedValue,
-        PyFormatContext<'ast>,
-    >;
-    fn into_format(self) -> Self::Format {
-        FormatOwnedWithRule::new(
-            self,
-            crate::expression::expr_formatted_value::FormatExprFormattedValue::default(),
-        )
-    }
-}
-
 impl FormatRule<ast::ExprFString, PyFormatContext<'_>>
     for crate::expression::expr_f_string::FormatExprFString
 {