Lintcheck: Rework and limit diff output for GH's CI
### Background
While working on https://github.com/rust-lang/rust-clippy/pull/13136 I found an amazing limitation of GH's CI. The summary can at most have be 1MB of text. Here is the warning message:
> $GITHUB_STEP_SUMMARY upload aborted, supports content up to a size of 1024k, got 46731k. For more information see: https://docs.github.com/actions/using-workflows/workflow-commands-for-github-actions#adding-a-markdown-summary
[The PR](https://github.com/rust-lang/rust-clippy/pull/13136) produced a *casual* 61808 changes. Guess that's why those lints are not *warn-by-default* :P.
### Changes:
This PR limits the lintcheck diff output in two ways.
1. The diff is limited to 200 messages per lint per section. Hidden messages are indicated by a message at the end of the section.
2. The output is first written to a file and only the first 1MB is written to ` >> $GITHUB_STEP_SUMMARY`. The entire file is also written to the normal CI log. This helps for cases where several lints change and the total size exceeds the 1MB limit.
An example of these changes can be seen here: https://github.com/xFrednet/rust-clippy/actions/runs/10028799118?pr=4
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changelog: none
r? `@Alexendoo`
Sorry for bombarding you with so many PR's lately 😅 Feel free to pass some of you reviews to me.
fix ice reporting in lintcheck
Fixes https://github.com/rust-lang/rust-clippy/issues/12185
This PR fixes the lack of reported ICEs within lintcheck by modifying the way in which data is collected from each crate being linted.
Instead of lintcheck only reading `stdout` for warnings, it now also reads `stderr` for any potential ICE (although admittedly, it is not the cleanest method of doing so). If it is detected, it parses the ICE into its message and backtrace separately, and then adds them to the list of outputs via clippy.
Once all outputs are collected, the formatter then proceeds to generate the file as normal.
Note that this PR also has a couple of side effects:
- When clippy fails to process a package, but said failure is not an ICE, the `stderr` will be sent to the console;
- Instead of `ClippyWarning` being the primary struct for everything reported, there is now `ClippyCheckOutput`, an enum which splits the outputs into warnings and ICEs.
changelog: none
