Auto merge of #148436 - jieyouxu:revert-unicode-generator, r=Zalathar

Revert "unicode_data refactors RUST-147622"

This PR reverts RUST-147622 for several reasons:

1. The RUST-147622 PR would format the generated core library code using an arbitrary `rustfmt` picked up from `PATH`, which will cause hard-to-debug failures when the `rustfmt` used to format the generated unicode data code versus the `rustfmt` used to format the in-tree library code produce incompatible formatting.
2. Previously, the `unicode-table-generator` tests were not run under CI as part of `coretests`, and since for `x86_64-gnu-aux` job we run library `coretests` with `miri`, the generated tests unfortunately caused an unacceptably large Merge CI time regression from ~2 hours to ~3.5 hours, making it the slowest Merge CI job (and thus the new bottleneck).
3. This PR also has an unintended effect of causing a diagnostic regression (RUST-148387), though that's mostly an edge case not properly handled by `rustc` diagnostics.

Given that these are three distinct causes with non-trivial fixes, I'm proposing to revert this PR to return us to baseline. **This is not prejudice against relanding the changes with these issues addressed, but to alleviate time pressure to address these non-trivial issues.**

FYI `@Kmeakin` `@joboet` (PR author/review). Note that these issues are very subtle, so you cannot be reasonably expected to know about them beforehand.

This was discussed in:

- [#t-infra/bootstrap > `unicode_data` refactors PR](https://rust-lang.zulipchat.com/#narrow/channel/326414-t-infra.2Fbootstrap/topic/.60unicode_data.60.20refactors.20PR/with/553360227)
- [#t-infra > x86_64-gnu-aux job went from ~2 to ~3.5 hours](https://rust-lang.zulipchat.com/#narrow/channel/242791-t-infra/topic/x86_64-gnu-aux.20job.20went.20from.20~2.20to.20~3.2E5.20hours/with/553354955)