uinput: pass Commands to Event.Builder.setCommand

Parsing strings into enum values should be done by the parser, not the
builder, and this means that the evemu parser will be able to pass
properly typed values to setCommand rather than "magic" strings.

Bug: 302297266
Test: m uinput
Change-Id: Icac5764a66025412c87c326280d1895f3da78cac