## Summary
This fixes two problems discovered when trying to format the cpython
repo with `cargo run --bin ruff_dev -- check-formatter-stability
projects/cpython`:
The first is to ignore try/except trailing comments for now since they
lead to unstable formatting on the dummy.
The second is to avoid dropping trailing if comments through placement:
This changes the placement to keep a comment trailing an if-elif or
if-elif-else to keep the comment a trailing comment on the entire if.
Previously the last comment would have been lost.
```python
if "first if":
pass
elif "first elif":
pass
```
The last remaining problem in cpython so far is function signature
argument separator comment placement which is its own PR on top of this.
## Test Plan
I added test fixtures of minimized examples with links back to the
original cpython location
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## Summary
This PR replaces the `verbatim_text` builder with a `not_yet_implemented` builder that emits `NOT_YET_IMPLEMENTED_<NodeKind>` for not yet implemented nodes.
The motivation for this change is that partially formatting compound statements can result in incorrectly indented code, which is a syntax error:
```python
def func_no_args():
a; b; c
if True: raise RuntimeError
if False: ...
for i in range(10):
print(i)
continue
```
Get's reformatted to
```python
def func_no_args():
a; b; c
if True: raise RuntimeError
if False: ...
for i in range(10):
print(i)
continue
```
because our formatter does not yet support `for` statements and just inserts the text from the source.
## Downsides
Using an identifier will not work in all situations. For example, an identifier is invalid in an `Arguments ` position. That's why I kept `verbatim_text` around and e.g. use it in the `Arguments` formatting logic where incorrect indentations are impossible (to my knowledge). Meaning, `verbatim_text` we can opt in to `verbatim_text` when we want to iterate quickly on nodes that we don't want to provide a full implementation yet and using an identifier would be invalid.
## Upsides
Running this on main discovered stability issues with the newline handling that were previously "hidden" because of the verbatim formatting. I guess that's an upside :)
## Test Plan
None?
