RFR: Fix a crash with IntelliJ 2020.2 [v2]

[Liam Miller-Cushon]

> com.intellij.diagnostic.PluginException: Class constructor must not have parameters: com.oracle.plugin.jtreg.service.ui.JTRegServiceConfigurable [Plugin: jtreg]
> 	at com.intellij.serviceContainer.ComponentManagerImpl.instantiateExtensionWithPicoContainerOnlyIfNeeded(ComponentManagerImpl.kt:696)
> 	at com.intellij.openapi.options.ConfigurableEP$ClassProducer.createElement(ConfigurableEP.java:422)
> 	at com.intellij.openapi.options.ConfigurableEP.createConfigurable(ConfigurableEP.java:329)
> 	at com.intellij.openapi.options.ex.ConfigurableWrapper.createConfigurable(ConfigurableWrapper.java:45)

Liam Miller-Cushon has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  Fix a crash with IntelliJ 2020.2
  
  ```
  com.intellij.diagnostic.PluginException: Class constructor must not have parameters: com.oracle.plugin.jtreg.service.ui.JTRegServiceConfigurable [Plugin: jtreg]
  	at com.intellij.serviceContainer.ComponentManagerImpl.instantiateExtensionWithPicoContainerOnlyIfNeeded(ComponentManagerImpl.kt:696)
  	at com.intellij.openapi.options.ConfigurableEP$ClassProducer.createElement(ConfigurableEP.java:422)
  	at com.intellij.openapi.options.ConfigurableEP.createConfigurable(ConfigurableEP.java:329)
  	at com.intellij.openapi.options.ex.ConfigurableWrapper.createConfigurable(ConfigurableWrapper.java:45)
  ```

-------------

Changes:
  - all: https://git.openjdk.java.net/jtreg/pull/5/files
  - new: https://git.openjdk.java.net/jtreg/pull/5/files/9d52c7e3..50996849

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jtreg&pr=5&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jtreg&pr=5&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod
  Patch: https://git.openjdk.java.net/jtreg/pull/5.diff
  Fetch: git fetch https://git.openjdk.java.net/jtreg pull/5/head:pull/5

PR: https://git.openjdk.java.net/jtreg/pull/5