Existing test framework should be pre-selected at the very first start

[Vassiliy-Kudryashov]

Description
For the first time default selection (JUnit 5) is provided even if JUnit4 or TestNG is configured for the project.

Expected behavior
To improve first-time use experience we have to detect and suggest (namely pre-select) existing test framework.

Environment

1. There is configured JUnit4/JUnit5 or TestNG in project.
2. There is no configured state for the plugin (the very first usage)

Potential alternatives

No alternatives

Context

'Generate tests with UtBot' dialog

[Vassiliy-Kudryashov]

Note, our default now is JUnit 5. Default values are not being stored in Xml (utbot-settings.xml) thus if all settings have default values the file itself won't be persisted. So we don't tell 'first time use' case from 'currently user prefers default settings' case.