Underscore and dot should be removed from the variables references labels

### Expected Behavior

Long story short: https://github.com/Kong/insomnia/issues/2942 - this ticked was closed and wasn't re-opened. There are certain observations related. Since the issue remains I believe a new ticked should be created.

Here some points:
- Combination of underscore and dot is a part of internal implementation and should not be printed out on labels by default
- There are no obstacles to use reference without this ugly prefix, simply typing {{VarName}} and this should be default behaviour
- Underscore and dot was introduced to resolve very specific issue which is not commonly used and because of that it should be optional
- Everybody agree that this is simply looks "dirty" and "ugly" inside such a beautiful product as Insomnia is.

### Actual Behavior

All variables are prefixed with "_." by default

### Reproduction Steps

_No response_

### Is there an existing issue for this?

- [X] I have searched the [issue tracker](https://www.github.com/Kong/insomnia/issues) for this problem.

### Additional Information

_No response_

### Insomnia Version

2023.2.0

### What operating system are you using?

macOS

### Operating System Version

macos

### Installation method

download from official website

### Last Known Working Insomnia version

_No response_

Start by reproducing the variable-reference label behavior in Insomnia 2023.2.0 on macOS, focusing on how labels display the "_." prefix. Trace the variable reference UI from the displayed label to its formatting logic, then verify that labels omit the prefix by default while references such as {{VarName}} continue to work.

Written by the indexing model from the issue text.