Use of deprecated APIs

[sgravrock]

IdeaJasmine uses several APIs that are deprecated by JetBrains and, in most cases, scheduled for removal:

• JsTestRunConfigurationProducer
• StringUtils
• PathKt.isFile

StringUtils and PathKt.isFile should be straightforward to replace. JsTestRunConfigurationProducer is more of a challenge because it's undocumented. Although JetBrains has given us advance warning of its removal, they haven't suggested a replacement. Historically there haven't been documented APIs for implementing test runner plugins, but maybe that has changed. The source code to the OSS plugins maintained by JetBrains might also be a useful source of information.