Add sample numbering option to View Results Tree

**Colin Jackson** ([Bug 52307](https://bz.apache.org/bugzilla//show_bug.cgi?id=52307&redirect=false)):
I often need to compare an entry in the View Results Tree component to a list of Thread-specific test data. This would be made much easier if the entries in the View Results Tree could be numbered. It is hard to identify the 1027th entry in the list in the current component, for example.

OS: All

Start by locating the View Results Tree component in the JMeter source and reading how its entries are currently displayed. Determine where an optional sample number belongs in that component, then verify that enabling it numbers entries consistently while leaving the existing display unchanged when disabled.

Written by the indexing model from the issue text.