[XGrid] Server-side filtering and multi-column filtering don't work well together

[jamintz]

• The issue is present in the latest release.
• I have searched the issues of this repository and believe that this is not a duplicate.

Current Behavior 😯

When running server-side filtering (eg the example given here) but changed to XGrid), if you press the "add filter" button in the panel it seems like nothing happens. No additional filter row is added as expected (and how it works in XGrid without server-side filtering).

Clicking elsewhere and then back to filter loads the filter panel again, it will now have N rows for every time you clicked "add filter" before

Expected Behavior 🤔

When pressing "add filter" while running server-side filtering in XGrid, an additional row should appear in the filter panel

Steps to Reproduce 🕹

Steps:

1. Load https://material-ui.com/components/data-grid/filtering/#server-side-filter locally or in codesandbox, using XGrid instead of DataGrid – example here: https://codesandbox.io/s/material-demo-forked-mv2xz?file=/demo.js
2. Filter the column
3. Press the "add filter" button
4. Observe no change to filter panel until you click elsewhere then back on filters

Context 🔦

A user should be able to both use server-side filtering and multi-column filtering nicely together

Your Environment 🌎

Observed using Chrome 88

 System:
    OS: macOS 11.1
  Binaries:
    Node: 15.8.0 - /usr/local/bin/node
    Yarn: 1.22.10 - /usr/local/bin/yarn
    npm: 7.5.0 - /usr/local/bin/npm
  Browsers:
    Chrome: 88.0.4324.150
    Edge: Not Found
    Firefox: 84.0.1
    Safari: 14.0.2
  npmPackages:
    @material-ui/core: ^4.11.3 => 4.11.3 
    @material-ui/icons: ^4.11.2 => 4.11.2 
    @material-ui/lab: ^4.0.0-alpha.57 => 4.0.0-alpha.57 
    @material-ui/styles:  4.11.3 
    @material-ui/system:  4.11.3 
    @material-ui/types:  5.1.0 
    @material-ui/utils:  4.11.2 
    @material-ui/x-grid: ^4.0.0-alpha.19 => 4.0.0-alpha.19 
    @material-ui/x-grid-data-generator: ^4.0.0-alpha.19 => 4.0.0-alpha.19 
    @material-ui/x-license:  4.0.0-alpha.19 
    @types/react:  17.0.1 
    react: ^17.0.1 => 17.0.1 
    react-dom: ^17.0.1 => 17.0.1 

[jamintz]

This is mostly resolved with a full implementation where it's actually updating on change, however it still may be useful to have a better / more complete example