…optimizations

This is another feature that we mentioned in the Eliminate Render Blocking Requests RFC (#18730)

Inlining of critical CSS is turned off by default. To opt-in this feature set `inlineCritical` to `true`.

Example:
```json
"configurations": {
  "production": {
    "fileReplacements": [
      {
        "replace": "src/environments/environment.ts",
        "with": "src/environments/environment.prod.ts"
      }
    ],
    "optimization": {
      "styles": {
        "minify": true,
        "inlineCritical": true,
       }
    },
```

To learn more about critical CSS see;
https://web.dev/defer-non-critical-css
https://web.dev/extract-critical-css/

In a future version of the Angular CLI `inlineCritical` will be enabled by default.

Closes: #17966
Closes: #11395
Closes: #19445