bug(cdk/scrolling): The append only mode assumes that scrolling starts at zero and therefore calculates renderedRange incorrectly

#### Reproduction

Steps to reproduce:
1. Create a virtual scroll container with `appendOnly`
2. Load the virtual scroll container and don't load it from the top
3. The `renderedRange` is wrongly calculated/set

#### Expected Behavior

A virtual scroll container can be loaded at any position without `renderedRange` being set incorrectly.

#### Actual Behavior

The `renderedRange` was set incorrectly once the virtual scroll container was loaded not at the top. I archived this behaviour via the following CSS setting.

```
[cdk-virtual-scroll-viewport] {
overflow-anchor: none;
}
```

#### A possible solution

I was able to solve this issue by overriding the following code at [virtual-scroll-viewport.ts#L292](https://github.com/angular/components/blob/6076801883194f263a5c692797ffc863a8de9771/src/cdk/scrolling/virtual-scroll-viewport.ts#L292)

```diff
if (this.appendOnly) {
- range = {start: 0, end: Math.max(this._renderedRange.end, range.end)};
+ range = {start: Math.min(this._renderedRange.start, range.start), end: Math.max(this._renderedRange.end, range.end)};
}
```

I am not sure if I am missing something. For this reason, I have just opened an issue and no pull request for now.

#### Environment

- Angular: 12.2.5
- CDK/Material: 12.2.5
- Browser(s): Chrome
- Operating System (e.g. Windows, macOS, Ubuntu): macOS

Inizia in src/cdk/scrolling/virtual-scroll-viewport.ts, intorno al calcolo dell'intervallo appendOnly alla riga 292, quindi riproduci il problema con un contenitore di scorrimento virtuale caricato in una posizione diversa da zero. Verifica che renderedRange conservi l'intervallo caricato inizialmente invece di presumere un inizio pari a zero; il lavoro è completato quando appendOnly funziona correttamente per questo caso.

Scritto dal modello di indicizzazione a partire dal testo della issue.