feat(progress-bar): Missing `--mdc-linear-progress-active-indicator-shape` property for progress-bar

### Feature Description

Currently if I want to change the shape of the progress bar to be round like, I only have the `--mdc-linear-progress-track-shape` to set the track shape, but not the same option for the shape of the active-indicator, which will still be square.
Also, only setting the `--mdc-linear-progress-track-shape`, will result in the active indicator overflowing, leaving me with an inconsistent progress-bar (see 1st picture)

Hence that leaves me with the better option of just setting the `border-radius` of the `mat-progress-bar` element itself, because this doesn't cause the active-indicator to overflow. In this case the `--mdc-linear-progress-track-shape` becomes redundant.

1. Screenshot with `--mdc-linear-progress-track-shape: 4px;`, causing the active-indicator to overflow:

2. Screenshot with `--mdc-linear-progress-track-shape: 4px;` and `border-radius: 4px`, rendering the `--mdc-linear-progress-track-shape` redundant:

3. Screenshot with only `border-radius: 4px;` leaving me with an almost round progress bar, except that the active-indicator is not actually round.

So there need to be an option to set the `--mdc-linear-progress-active-indicator-shape` like for other components, so that the active-indicator can be made round, as shown in the [Token and Specs section in the Material 3 specification](https://m3.material.io/components/progress-indicators/specs)

### Use Case

This would enable a very relevant an normal use case that is also shown in the [Token and Specs section in the Material 3 specification](https://m3.material.io/components/progress-indicators/specs).

从 progress-bar 组件开始，跟踪 --mdc-linear-progress-track-shape 如何应用于轨道和活动指示器。将其样式与 Material 3 progress-indicator 的 Token and Specs 部分进行比较，然后验证新的 active-indicator shape option 是否能在不发生溢出的情况下使指示器变圆角。

由索引模型根据 Issue 内容生成。