Given:
```python
x: DataFrame[
int
] = 1
```
We currently wrap the annotation in single quotes, which leads to a
syntax error:
```python
x: "DataFrame[
int
]" = 1
```
There are a few options for what to suggest for users here... Use triple
quotes:
```python
x: """DataFrame[
int
]""" = 1
```
Or, use an implicit string concatenation (which may require
parentheses):
```python
x: ("DataFrame["
"int"
"]") = 1
```
The solution I settled on here is to use the `Generator`, which
effectively means we write it out on a single line, like:
```python
x: "DataFrame[int]" = 1
```
It's kind of the "least opinionated" solution, but it does mean we'll
expand to a very long line in some cases.
Closes https://github.com/astral-sh/ruff/issues/9136.
d1a7bc38ff