Rewrite ecosystem checks and add ruff format reports (#8223)

Closes #7239 

- Refactors `scripts/check_ecosystem.py` into a new Python project at
`python/ruff-ecosystem`
- Includes
[documentation](https://github.com/astral-sh/ruff/blob/zanie/ecosystem-format/python/ruff-ecosystem/README.md)
now
    - Provides a `ruff-ecosystem` CLI
- Fixes bug where `ruff check` report included "fixable" summary line
- Adds truncation to `ruff check` reports
    - Otherwise we often won't see the `ruff format` reports
- The truncation uses some very simple heuristics and could be improved
in the future
- Identifies diagnostic changes that occur just because a violation's
fix available changes
- We still show the diff for the line because it's could matter _where_
this changes, but we could improve this
- Similarly, we could improve detection of diagnostic changes where just
the message changes
- Adds support for JSON ecosystem check output
    - I added this primarily for development purposes
- If there are no changes, only errors while processing projects, we
display a different summary message
- When caching repositories, we now checkout the requested ref
- Adds `ruff format` reports, which format with the baseline then the
use `format --diff` to generate a report
- Runs all CI jobs when the CI workflow is changed

## Known problems

- Since we must format the project to get a baseline, the permalink line
numbers do not exactly correspond to the correct range
- This looks... hard. I tried using `git diff` and some wonky hunk
matching to recover the original line numbers but it doesn't seem worth
it. I think we should probably commit the formatted changes to a fork or
something if we want great results here. Consequently, I've just used
the start line instead of a range for now.
- I don't love the comment structure — it'd be nice, perhaps, to have
separate headings for the linter and formatter.
- However, the `pr-comment` workflow is an absolute pain to change
because it runs _separately_ from this pull request so I if I want to
make edits to it I can only test it via manual workflow dispatch.
- Lines are not printed "as we go" which means they're all held in
memory, presumably this would be a problem for large-scale ecosystem
checks
- We are encountering a hard limit with the maximum comment length
supported by GitHub. We will need to move the bulk of the report
elsewhere.

## Future work

- Update `ruff-ecosystem` to support non-default projects and
`check_ecosystem_all.py` behavior
- Remove existing ecosystem check scripts
- Add preview mode toggle (#8076)
- Add a toggle for truncation
- Add hints for quick reproduction of runs locally
- Consider parsing JSON output of Ruff instead of using regex to parse
the text output
- Links to project repositories should use the commit hash we checked
against
- When caching repositories, we should pull the latest changes for the
ref
- Sort check diffs by path and rule code only (changes in messages
should not change order)
- Update check diffs to distinguish between new violations and changes
in messages
- Add "fix" diffs
- Remove existing formatter similarity reports
- On release pull request, compare to the previous tag instead

---------

Co-authored-by: konsti <konstin@mailbox.org>

python/ruff-ecosystem/ruff_ecosystem/markdown.py

@@ -0,0 +1,44 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from ruff_ecosystem.projects import Project
+
+
+def markdown_project_section(
+    title: str, content: str | list[str], options: object, project: Project
+) -> list[str]:
+    return markdown_details(
+        summary=f'<a href="{project.repo.url}">{project.repo.fullname}</a> ({title})',
+        # Show the command used for the check
+        preface="<pre>ruff " + " ".join(options.to_cli_args()) + "</pre>",
+        content=content,
+    )
+
+
+def markdown_plus_minus(added: int, removed: int) -> str:
+    # TODO(zanieb): GitHub does not support coloring with <span> it seems like the only
+    #               way is to use LateX `${\text{\color{green}+10 \color{red}-10}}$` but
+    #               it renders so ugly it's not worth doing yet
+    return f"+{added} -{removed}"
+
+
+def markdown_details(summary: str, preface: str, content: str | list[str]):
+    lines = []
+    lines.append(f"<details><summary>{summary}</summary>")
+    lines.append("<p>")
+    lines.append(preface)
+    lines.append("</p>")
+    lines.append("<p>")
+    lines.append("")
+
+    if isinstance(content, str):
+        lines.append(content)
+    else:
+        lines.extend(content)
+
+    lines.append("")
+    lines.append("</p>")
+    lines.append("</details>")
+    return lines