Reorganize some JSX-related tests

[Andarist]

After switching completely to the -experimental helper the current directories didn't make sense in some cases. next* directories were responsible for testing the -experimental helper because it was complete overwrite of the implementation - this made sense at the time they have been introduced. Both nextReact and nextReactClassic had mainly the same tests that were already in the react directory.

What has been done:

1. I've recognized which tests were in the nextReactClassic dir and not in the react dir and just moved those extras to the react dir. Note: nextReactClassic was actually using automatic runtime through an option (to opt into the -experimental helper) and "switched back" to the classic runtime through a @jsxRuntime pragma. I don't think this was an important distinction so the moved tests just use the classic runtime through a default option.
2. I've removed the nextReactClassic completely as those tests are IMHO already covered by the react directory
3. I've renamed nextReact to react-automatic (in Babel 8 the names probably should be switch, react should become react-classic and react-automatic should become just react). I've decided to keep this directory - it tests pretty much the same thing as react dir - just with the automatic runtime. It really shouldn't matter much and if I would implement this from scratch I probably wouldn't duplicate those tests for both runtimes but as we already have them I don't think it's worth removing them.
4. I've renamed nextAutoImport to autoImport - this seems like its own category of tests, so worth keeping them separately
5. I've moved tests related to @babel/transform-react-display-name to its package - I think it makes more sense to keep them there than in the main package.

[babel-bot]

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[nicolo-ribaudo]

Thanks!