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

Nadie ha tomado este issue todavía.

#### 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

Comienza en src/cdk/scrolling/virtual-scroll-viewport.ts, alrededor del cálculo del rango de appendOnly en la línea 292, y reproduce el problema con un contenedor de desplazamiento virtual cargado en una posición distinta de cero. Verifica que renderedRange conserve el rango cargado inicialmente en lugar de asumir un inicio de cero; el trabajo estará terminado cuando appendOnly funcione correctamente para ese caso.

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