[material-ui][Hidden] Remove deprecated Hidden component

[DiegoAndai]

Closes #44073
First attempt: #42305

Remove the deprecated Hidden component as well as its pigment counterpart.

[mui-bot]

Netlify deploy preview

• docs/data/material/migration/upgrade-to-v7/upgrade-to-v7.md

Hidden: parsed: -100.00% 😍, gzip: -100.00% 😍
PigmentHidden: parsed: -100.00% 😍, gzip: -100.00% 😍
@material-ui/core: parsed: -0.68% 😍, gzip: -1.15% 😍

Bundle size report

Details of bundle changes (Toolpad)
Details of bundle changes

Generated by 🚫 dangerJS against e431496

[DiegoAndai]

@aarongarciah I went through the rabbit hole of trying to implement a codemod for this. Bottom line: I don't think it's worth the complexity:

• The 'js' implementation (which is the default) is quite complicated to codemod, and prone to errors. It depends too much on the user's codebase
• The 'css' implementation is possible, but there are a lot of edge cases and chances for it to go wrong: No children, multiple children, children which support sx, children that don't support sx, children with existing sx prop`.

I think it's better to add a warning and for users to migrate this manually; the codemod would barely cover one implementation ('css') and it wouldn't do a great job on that one either. What do you think?

[aarongarciah]

@DiegoAndai I think the upgrade guide is enough.

[aarongarciah]

🧹🙌