MINOR: htx: Rename htx_has_eom() into htx_msg_ended()

MINOR: htx: Rename htx_has_eom() into htx_msg_ended()

htx_has_eom() name suggests the HTX message contains a block carrying the
HTX_BLK_FL_EOM flag. It is true for now, because the flag can only be found
on the tail block. But this will change. The block carrying this flag may be
consumed while the end of the message must still be reported. So the name is
misleading and htx_msg_ended() is more accurate: it states the end of the
message was reached, regardless of the presence of the flag in the message.

Only a rename, there is no change of behavior. Note the sample fetch
"internal.htx.has_eom" was not renamed because it is part of the
configuration.