[DataGrid] Remove dependency on lodash

[oliviertassinari]

While lodash was inlined in the repository (I guess to hide, on the surface, the dependency on this library), I don't think that it removes the fact that we depend on it. I would be in favor of completely removing its modules from the codebase.

Possible migration plan:

• denounce. Instead of the 938 B version of lodash we could rely on the 305 B import { denounce } from @material-ui/core module. We could also move the module to @material-ui/utils instead of the core if that makes more sense. This module also has the advantage of being deduplicated with the core components, sharing the simple source.
• deep equal. Instead of the 3.8 Kb version of lodash, we could replace it with fast-deep-equal, a 414 B alternative. I have only seen one use case in the codebase, I even wonder if we couldn't use JSON.stringify directly.

https://github.com/mui-org/material-ui-x/blob/fb5af45b5d74ca818fc6945af17400cec0ee21a2/packages/grid/src/hooks/root/useColumns.tsx#L162

[oliviertassinari]

Closing for #18