User defined variable of the last thread overrides the predecessor thread user defined variable

### Expected behavior

The user defined variables that are defined under thread group should have the scope with in the respective thread group.

### Actual behavior

When tester is having 2 scripts with 2 different login urls and the tester combines them in same test plan notice some of the general user defined variables like P_url which is different for each of the scripts fails to work as the P_url defined in the 2nd thread group overrides the P_url defined in the 1st thread group.

### Steps to reproduce the problem

[JMeter_Bug2.docx](https://github.com/user-attachments/files/21577453/JMeter_Bug2.docx)

- User created 2 thread groups
- Each thread group has user defined variable element
- The name of variable P_url is used to parameterize the url of the request
- P_url in the thread group 1 holds the value of 1st application url
- P_url in the thread group 2 holds the value of 2nd application url
- When user runs the test notice that P_url value in thread group 1 is overwritten by 2nd application url
- Refer the document provided

### JMeter Version

5.5

### Java Version

openjdk-17.0.14

### OS Version

Windows Server 2022 Datacenter 21H2