[MaterialButton] Padding is incorrect when using `iconGravity` is `end`/`textEnd`

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**Description:** `MaterialButton` supports moving the icon to the end of the button or the button text by setting `iconGravity` to `end` or `textEnd`. The padding that `Widget.Material3.Button.Icon` adds however assumes the icon is at the start of the start of the text of the button (`start` or `textStart`). As an example, here's a button using `Widget.Material3.Button.Icon` with `iconGravity` set to `textEnd`:

**Expected behavior:** It would be amazing if `MaterialButton` (or the `Widget.Material3.Button.x` styles) were able to dynamically switch the padding based on the `iconGravity`, but I'm not sure how feasible that is. Alternatively, MaterialComponents could provide a style (or a theme overlay) for end icons like:

```xml

<item name="android:paddingStart">@dimen/m3_btn_icon_btn_padding_right</item>
<item name="android:paddingEnd">@dimen/m3_btn_icon_btn_padding_left</item>
<item name="iconGravity">end</item>

```

**Material Library version:** 1.9.0

Start at MaterialButton and the Widget.Material3.Button.Icon style resources; compare how padding is assigned for iconGravity start/textStart versus end/textEnd. Reproduce the shown textEnd layout and verify the resulting button padding for both end modes, with coverage if the existing component tests cover these styles.

Written by the indexing model from the issue text.