Add a differentiator for checkboxes that can contain expressions.

### Use case

Since 5.6.x some checkboxes could be change in an expression (right click on checkbox) but there is no external information to explains if the checkbox is "standard" or "expression compatible".

https://github.com/apache/jmeter/pull/6199


### Possible solution

1- First solution : Add some text between the checkbox and the label.
E.g.1 Test Plan :
Before : "Run Thread Groups consecutively"
After : " (Exp) Run Thread Groups consecutively" , add **(Exp)** in the label to explain that checkbox is **Exp**ression compatible.

E.g.2 Test Plan :
Before : "Delay Thread creation until needed"
After : "(Exp) Delay Thread creation until needed"

2-Second solution : Change the color background of the checkbox compatible with expression
E.g.3 Thread Group :
cb.setBackground(Color.ORANGE);
cb.setOpaque(true);


### Possible workarounds

_No response_

### JMeter Version

5.6.3

### Java Version

jdk8 to jdk17

### OS Version

All OS