The previous name for this was rather misleading. It isn't an actual
jump like you'd expect the `jp` instruction to behave as. Instead, it
behaves more like a `farcall`.
This also makes it consistent with its current command ID name of
`TX_FAR`.
Some of the TX_ commands didn't use the TX_ prefix for their
constants, and the label names were inconsistent. I've chosen to adopt
the `TextCommand_` prefix as opposed to `Text_`, as it has a clear
difference in namespace compared to the possibly-used `Text_` namespace
for actual dialogue text.
