Compiletest Directives: Output Normalization and Rustfix

3rd chunk of `src/tests/directives.md`

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|-----------------------------------|--------------------------------------------------------------------------------------------------------------------------|----------------------------------------------|-----------------------------------------------------------------------------------------|
| `check-run-results`               | Check run test binary `run-{pass,fail}` output snapshot                                                                  | `ui`, `crashes`, `incremental` if `run-pass` | N/A                                                                                     |
| `error-pattern`                   | Check that output contains a specific string                                                                             | `ui`, `crashes`, `incremental` if `run-pass` | String                                                                                  |
| `regex-error-pattern`             | Check that output contains a regex pattern                                                                               | `ui`, `crashes`, `incremental` if `run-pass` | Regex                                                                                   |
| `check-stdout`                    | Check `stdout` against `error-pattern`s from running test binary[^check_stdout]                                          | `ui`, `crashes`, `incremental`               | N/A                                                                                     |
| `normalize-stderr-32bit`          | Normalize actual stderr (for 32-bit platforms) with a rule `"<raw>" -> "<normalized>"` before comparing against snapshot | `ui`, `incremental`                          | `"<RAW>" -> "<NORMALIZED>"`, `<RAW>`/`<NORMALIZED>` is regex capture and replace syntax |
| `normalize-stderr-64bit`          | Normalize actual stderr (for 64-bit platforms) with a rule `"<raw>" -> "<normalized>"` before comparing against snapshot | `ui`, `incremental`                          | `"<RAW>" -> "<NORMALIZED>"`, `<RAW>`/`<NORMALIZED>` is regex capture and replace syntax |
| `normalize-stderr`                | Normalize actual stderr with a rule `"<raw>" -> "<normalized>"` before comparing against snapshot                        | `ui`, `incremental`                          | `"<RAW>" -> "<NORMALIZED>"`, `<RAW>`/`<NORMALIZED>` is regex capture and replace syntax |
| `normalize-stdout`                | Normalize actual stdout with a rule `"<raw>" -> "<normalized>"` before comparing against snapshot                        | `ui`, `incremental`                          | `"<RAW>" -> "<NORMALIZED>"`, `<RAW>`/`<NORMALIZED>` is regex capture and replace syntax |
| `dont-check-compiler-stderr`      | Don't check actual compiler stderr vs stderr snapshot                                                                    | `ui`                                         | N/A                                                                                     |
| `dont-check-compiler-stdout`      | Don't check actual compiler stdout vs stdout snapshot                                                                    | `ui`                                         | N/A                                                                                     |
| `dont-require-annotations`        | Don't require line annotations for the given diagnostic kind (`//~ KIND`) to be exhaustive                               | `ui`, `incremental`                          | `ERROR`, `WARN`, `NOTE`, `HELP`, `SUGGESTION`                                           |
| `run-rustfix`                     | Apply all suggestions via `rustfix`, snapshot fixed output, and check fixed output builds                                | `ui`                                         | N/A                                                                                     |
| `rustfix-only-machine-applicable` | `run-rustfix` but only machine-applicable suggestions                                                                    | `ui`                                         | N/A                                                                                     |

Title: Compiletest Directives: Output Normalization and Rustfix

Summary

This section details compiletest directives for controlling output normalization and applying Rustfix. It includes directives like `check-run-results`, `error-pattern`, `regex-error-pattern`, `check-stdout`, `normalize-stderr-*`, `normalize-stdout`, and directives to control compiler stdout/stderr checks. It also covers directives related to Rustfix, such as `run-rustfix` and `rustfix-only-machine-applicable`, for applying suggestions and verifying builds.