Improve menu icons/symbols

### Is there an existing issue for this?

- [x] I have searched the existing issues and checked the recent builds/commits

### What problem are you experiencing?

Some of the menu icons are generic and could be improved. Creates a challenge when trying to find what you're looking for.

### When does this problem occur?

When navigating menus

### How often do you encounter this problem?

Multiple times per day

### How much does this problem affect your workflow?

Minor annoyance

### Current workarounds

Squint to read the text

### Ideas for solutions (Optional)

Text:

> Chains are associated with the concept of chaining, we want the user to think "node" not "chain". The center circle is large enough to indicate that the main idea is the object being represented, not the concept being represented.
>
> The unet is an easily recognizable anachronism similar to a telephone receiver. The current symbol reads more like "one is not like the other 3" which indicates specialty, but isn't very specific.
>
> The top-down flowchart symbol is currently used for subgraphs, which are also workflows. Using the same symbol for both can help the user recognize the intended nature of subgraphs more easily.
>
> "Cookie cutter" is a phrase that means "to replicate". What better symbol to use here than the gingerbread man? The concept is already >>baked<< into culture, making it easily recognizable.

### Additional context

I have inkscape. If you're open to it, I could take a stab at polishing some of these (if they don't already exist or you don't have a graphic artist). I hope this problem isn't just me lol.

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-6111-Improve-menu-icons-symbols-28f6d73d365081aebe8af79b7b3ec1b7) by [Unito](https://www.unito.io)