[Feature]: Allow for string widgets on subgraphs to be set to either multiline or singleline

### 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?

Currently on subgraphs, the widget type of a string (multiline or singleline) is tied solely to the widget on the node it's connected to.

### When does this problem occur?

For example purposes, let's take a look at a simple case of this, we will take a CLIP Text Encode node, and connect it up in a subgraph situation.

Well, we have no way at all to set this to being just a singleline string by itself.

### How often do you encounter this problem?

Occasionally

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

Minor annoyance

### Current workarounds

A simple workaround for example is to tie the multiline widget to a singleline string primitive as follows:

And vice versa. However, it would be a much more convenient solution if this could be done on the subgraph connector itself.

### Ideas for solutions (Optional)

Firstly, considering that multiline strings and singleline strings appear to create two different types of inputs for the subgraph, this should be unified into one type.

When implemented:

1. Right click on a subgraph input slot containing a string primitive
2. Click "Make Singleline" or "Make Multiline"

### Additional context

_No response_

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-5028-Feature-Allow-for-string-widgets-on-subgraphs-to-be-set-to-either-multiline-or-sing-2506d73d3650810f9453cf2a913e3fbb) by [Unito](https://www.unito.io)

No files or tests are named. Start by reproducing the CLIP Text Encode subgraph example and trace how subgraph input slots derive string widget types from connected nodes. Implement the requested “Make Singleline” and “Make Multiline” actions on string primitive inputs, then verify both modes work without the described primitive workaround.

Written by the indexing model from the issue text.