Update Hydra documentation links to the new OmegaConf website #3532

Hydra's current and archived documentation still contains 66 links to OmegaConf on Read the Docs. OmegaConf's current documentation is now hosted at https://omegaconf.cli.dev.

Update the 65 links targeting the old latest docs to the corresponding pages on the new site, including config access, interpolation, resolvers, structured configs, unions, and configuration flags. Map anchors to their new sections instead of replacing only the domain.

Preserve the archived Hydra 1.0 tutorial's explicit OmegaConf 2.0 link: the new site does not host that version. The two OmegaConf 2.4 migration links already use the new domain.

Verify the destination pages and anchors and run the production website build.