[v6] Upgrade minimum version of Node.js

[ZeeshanTamboli]

Summary 💡

Node v12 has reached end-of-life rather its ended. https://nodejs.org/en/about/releases/

material-ui/packages/mui-material/package.json

Lines 112 to 113 in ac99485

	"engines": {
	"node": ">=12.0.0"

Examples 🌈

Similar to dropping support for node v10 in #25306.

Motivation 🔦

1. Upgrade CI docker node image etc.

[ZeeshanTamboli]

cc: @mui/core

[michaldudak]

We can use a recent Node version for building the library, but I'd leave Node 12 for tests as we still support it. We will likely drop support for it with the next major version.

[ZeeshanTamboli]

We will likely drop support for it with the next major version.

Maybe we should link this issue in the next major version roadmap. Or somewhere else.