[kbn/plugin-generator] remove sao, modernize

[spalger]

I'm working on #63069 and keep running into the nasty edges of the old plugin generator. The generator is currently based https://saojs.org/ v0.22, and while they're working on a v2 of the library there isn't any typescript support, and I think it's a somewhat unnecessary dependency.

Instead, the plugin generator just uses vinyl-fs to operate on the files in the template directory, processing .ejs files with ejs, filtering out files based on what type of plugin is requested, and then passing all compatible files through prettier, before writing to the target location. This happens nice and quick, and without needing a bunch of dependencies that SAO was installing.

Additional QOL changes:

• ask for the name of the plugin if it's not provided on the CLI
• new -y flag to use the defaults, like yarn init -y, requires passing the name via the CLI
• removed "customPath" logic, instead we ask if the plugin is internal and ask which type of internal plugin when y is supplied.

[elasticmachine]

Pinging @elastic/kibana-operations (Team:Operations)

[cchaos]

👍 for design. Just moves a single .scss file

[tylersmalley]

LGTM - pretty amazing how much faster it is as well.

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: 07f5227

Build metrics

✅ unchanged

History

• 💚 Build #69509 succeeded 5b0d5d3
• 💚 Build #69427 succeeded d44c696
• 💚 Build #69278 succeeded d7bb31cb2f0ba124d9385ccd08df058921773d18
• 💔 Build #69276 failed 3e57e3f58fa81eedd6b65ffb41c83cab5d0baa15
• 💚 Build #69252 succeeded cf0855558138859246b81caf613faecdca044303

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@elasticmachine merge upstream