Rollup merge of #154754 - Kobzol:build-manifest-enzyme, r=Mark-Simulacrum,ZuseZ4

Add Enzyme to build-manifest and rustup

This PR adds the autodiff component (Enzyme) to build-manifest, and thus also to (nightly) Rustup.

It is marked as nightly-only and as -preview.

After this PR lands, unless I messed something up, starting with the following nightly, the following should work (on supported targets):

```bash
rustup +nightly component add enzyme
RUSTFLAGS="-Zautodiff=Enable" cargo +nightly build
```

CC @ZuseZ4

r? @Mark-Simulacrum

closes: https://github.com/rust-lang/rust/issues/145899