Render self argument connections as arrows

[AdRiley]

Update the self argument connections as per the figma design.

So instead of seeing operator12345

we get an arrow

### Tasks
- [ ] https://github.com/enso-org/enso/pull/9099
- [ ] https://github.com/enso-org/enso/pull/9116

[Frizi]

Refinement notes:

• The arrow should appear only in the most obvious case: method call with a "self" argument placed the access chain
• The icon should become a port to which you can connect a different "self" value
• The icon should still behave as a drag handler for the node when we are not dragging any connections

[enso-bot[bot]]

Keziah Wesley reports a new STANDUP for today (2024-02-19):

Progress: Implemented edge-rendering mode for self-arrows. It should be finished by 2024-02-23.

Next Day: Next day I will be working on the #9064 task. Refactoring to enable node icons to be ports.

[enso-bot[bot]]

Keziah Wesley reports a new STANDUP for today (2024-02-20):

Progress: Finished self-arguments feature. It should be finished by 2024-02-21.

Next Day: Next day I will be working on the #9064 task. Address review, pick something new from backlog.