Selective icon groups

### Is your feature request related to a problem? Please describe.
I just upgraded to 0.64.0 and added `nerdFontsVersion: "3"`. I now see icons for PRs and filetypes, which is cool, but now there are also commit icons (I guess regular vs. merge commit?).

Personally I find they make it a bit harder to read/skim the commits, and don't provide any additional information (I can see that there was a merge commit because of the icons between the SHA and the commit msg).

|Before | After |
| --- | --- |
| | |

### Describe the solution you'd like
I can't find in the config docs a way to disable those icons. Would it be possible to add a config to do that (and ideally enable/disable icon groups independently so the user can e.g. enable icons for PRs but not for files or commits)?

### Describe alternatives you've considered
N/A

### Additional context
N/A

Start by reading the configuration documentation and locating the existing Nerd Fonts and icon settings. Then trace how commit, pull request, and filetype icons are selected. Done means users can enable or disable these icon groups independently and the available settings are documented.

Written by the indexing model from the issue text.