Implement RUF027: Missing F-String Syntax lint (#9728)

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## Summary

Fixes #8151

This PR implements a new rule, `RUF027`.

## What it does
Checks for strings that contain f-string syntax but are not f-strings.

### Why is this bad?
An f-string missing an `f` at the beginning won't format anything, and
instead treat the interpolation syntax as literal.

### Example

```python
name = "Sarah"
dayofweek = "Tuesday"
msg = "Hello {name}! It is {dayofweek} today!"
```

It should instead be:
```python
name = "Sarah"
dayofweek = "Tuesday"
msg = f"Hello {name}! It is {dayofweek} today!"
```

## Heuristics
Since there are many possible string literals which contain syntax
similar to f-strings yet are not intended to be,
this lint will disqualify any literal that satisfies any of the
following conditions:
1. The string literal is a standalone expression. For example, a
docstring.
2. The literal is part of a function call with keyword arguments that
match at least one variable (for example: `format("Message: {value}",
value = "Hello World")`)
3. The literal (or a parent expression of the literal) has a direct
method call on it (for example: `"{value}".format(...)`)
4. The string has no `{...}` expression sections, or uses invalid
f-string syntax.
5. The string references variables that are not in scope, or it doesn't
capture variables at all.
6. Any format specifiers in the potential f-string are invalid.

## Test Plan

I created a new test file, `RUF027.py`, which is both an example of what
the lint should catch and a way to test edge cases that may trigger
false positives.

crates/ruff_linter/src/codes.rs

@@ -937,6 +937,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Ruff, "024") => (RuleGroup::Preview, rules::ruff::rules::MutableFromkeysValue),
         (Ruff, "025") => (RuleGroup::Preview, rules::ruff::rules::UnnecessaryDictComprehensionForIterable),
         (Ruff, "026") => (RuleGroup::Preview, rules::ruff::rules::DefaultFactoryKwarg),
+        (Ruff, "027") => (RuleGroup::Preview, rules::ruff::rules::MissingFStringSyntax),
         (Ruff, "100") => (RuleGroup::Stable, rules::ruff::rules::UnusedNOQA),
         (Ruff, "200") => (RuleGroup::Stable, rules::ruff::rules::InvalidPyprojectToml),
         #[cfg(feature = "test-rules")]