Virtual scroll collectionViewer.viewChange does not emit when direction is 'rtl'

### Is this a regression?

- [ ] Yes, this behavior used to work in the previous version

### The previous version in which this bug was not present was

_No response_

### Description

I'm using a `cdk-virtual-scroll-viewport` with `dir='rtl'`, connected to a _CdkDataSrouce_. When scrolling, the `viewChange` event is not emmited, and though I can't load more items as I go. The same code works if I change the direction to `ltr`.

### Reproduction

My template looks like this:
```

```

=> where `dataConnector` is my extension of a `CdkDataSrouce`

I think it might be related to having a negative `scrollOffset` when in `rtl` direction.

### Expected Behavior

I am expecting `collectionViewer.viewChange` to fire when I scroll to the left.

### Actual Behavior

It does not fire if the `dir` property is `rtl`

### Environment

- Angular: 12.0.4
- CDK/Material: 12.0.4
- Browser(s): Chrome Version 97.0.4692.71 (Official Build) (64-bit)
- Operating System (e.g. Windows, macOS, Ubuntu): Windows 10 64-bit

Start with the cdk-virtual-scroll-viewport behavior described in the reproduction and trace how RTL scrolling, negative scrollOffset values, and collectionViewer.viewChange interact. Reproduce the supplied template with Angular/CDK 12.0.4, then verify that scrolling left in rtl emits viewChange so additional items can load.

Written by the indexing model from the issue text.