improve git commit / commit all action icons

### Description

At the moment the icons for **commit** and **commit all** are identical:


Since I have both in a toolbar it would be nice to recognize the commit type from the icon.

### Use case/motivation

_No response_

### Related issues

_No response_

### Are you willing to submit a pull request?

No

Start at the Git UI's commit and commit-all toolbar actions and trace where their currently identical icon is defined. Choose distinct icons that make the two actions recognizable, then verify both actions display correctly together in the toolbar.

Written by the indexing model from the issue text.