Handle pattern parentheses in `FormatPattern` (#6800)
## Summary
This PR fixes the duplicate-parenthesis problem that's visible in the
tests from https://github.com/astral-sh/ruff/pull/6799. The issue is
that we might have parentheses around the entire match-case pattern,
like in `(1)` here:
```python
match foo:
case (1):
y = 0
```
In this case, the inner expression (`1`) will _think_ it's
parenthesized, but we'll _also_ detect the parentheses at the case level
-- so they get rendered by the case, then again by the expression.
Instead, if we detect parentheses at the case level, we can force-off
the parentheses for the pattern using a design similar to the way we
handle parentheses on expressions.
Closes https://github.com/astral-sh/ruff/issues/6753.
## Test Plan
`cargo test`
