Include actual conditions in E712 diagnostics (#10254)
## Summary
Changes the generic recommendation to replace
```python
if foo == True: ...
```
with `if cond:` to `if foo:`.
Still uses a generic message for compound comparisons as a specific
message starts to become confusing. For example,
```python
if foo == True != False: ...
```
produces two recommendations, one of which would recommend `if True:`,
which is confusing.
Resolves [recommendation in a previous
PR](https://github.com/astral-sh/ruff/pull/8613/files#r1514915070).
## Test Plan
`cargo nextest run`
