sysctl: improve PDO selection, USB PD handling

Chris Hofstaedtlerrequested to merge
zeha/pocket-reform:zeha/pdoselect-power into main

Improve PDO selection to favour higher maximum power, but still favouring >= 9V.

Correctly identify most messages, incl. GoodCRC which we can ignore for now. Reply to Discover_Identity to improve handshaking with some (notably Apple) chargers.

Edited by Chris Hofstaedtler

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