Updated some UM boards info

[UnexpectedMaker]

Also renamed tinypico to um_tinypico to match all of the UM board naming. These have been named this way in Arduino for a long time now.

[valeros]

Hi @UnexpectedMaker, thanks for the PR. The name of the manifest file plays an important role as a board ID in project configurations. It means that your simple renaming tinypico.json to um_tinypico.json may break already configured projects. If you insist on renaming, I'd recommend keeping both files tinypico.json an um_tinypico.json, but the name of the board in the tinypico.json file may contain a phrase like Unexpected Maker TinyPICO (deprecated in favor of "um_tinypico"), so that it can be safely removed in a new major release.

[UnexpectedMaker]

@valeros Oh, that's a really good point. I'll revert this change later today, and leave it as is.

[stale]

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