merge properties which have same properties name by config

[ibingdian]

Description

Add 1 configurable parameter to merge string-property which have same name. the value of configurable parameter is Separate with commas. Parameters are defined in jmeter.properties file. eg,merge.property=HTTPSampler.path

Motivation and Context

in multi ConfigTestElement, if we have same properties name, now is use pre value and no merge. but someties we may need common prefix ,the common prefix often changed by tester, and many HTTPSampler may use it. eg, the full http url is http://192.168.8.110:8088/local-xxx/xxx/mo/knowledge.json, other http url have the same prefix:/local-xxx/xxx, we can config a globe ConfigTestElement with a property [HTTPSampler.path=/local-xxx/xxx], then the [HTTPSampler.path] will merged to HTTPSampler .

How Has This Been Tested?

Run with multiple values in the .properties file, see the outcome.

Screenshots (if appropriate):

1 and 2 will be merge, as 3.

Types of changes

• New feature

Checklist:

• [ ] My code follows the code style of this project.
• [ ] I have updated the documentation accordingly.

[vlsi]

Have you considered using ${prefix}auth/login instead? I do not think the suggested "merge" is intuitive