Add consistency for reporting TestNG results for data providers

Summary

Overall, great experience working with vscode and this extension thus far. Adding this feature/fixing the bug (eye of the beholder) will save a bit of time running commands in the terminal to get reliable results.

See below for a depiction of the disagreement between the user interface and console reports as well as a simple reproduce case.

I'd imagine there are many ways to approach this for full flexibility but I do think having the default test listener support this out of the box and at least have agreement in counts would be a desirable feature. I have used other IDEs and here is one way it is being approached: https://github.com/JetBrains/intellij-community/blob/2aa816fb814bb07c697a17d6a27e427e142a3633/plugins/testng_rt/src/com/intellij/rt/testng/IDEATestNGRemoteListener.java.

Note: there are ways to work around this by implementing the ITest interface per test and overriding the getTestName method but this is cumbersome as well!

System and application versions

Version: 1.37.1 (user setup)
Commit: f06011ac164ae4dc8e753a3fe7f9549844d15e35
Date: 2019-08-15T16:17:55.855Z
Electron: 4.2.7
Chrome: 69.0.3497.128
Node.js: 10.11.0
V8: 6.9.427.31-electron.0
OS: Windows_NT x64 10.0.18362

TestNG version

  <dependency>
            <groupId>org.testng</groupId>
            <artifactId>testng</artifactId>
            <version>6.8</version>
            <scope>test</scope>
  </dependency>

Repro case

从默认的 TestNG listener 和 data provider 的 reporting 路径入手；issue 中的 ITest/getTestName workaround 以及链接的 IntelliJ listener 可作为对比点。复现 issue 中的情况，并验证 VS Code UI 和控制台报告的测试数量一致。