Turn off the MWS_FAINT target classes.

[geordie666]

This PR turns off all aspects of the MWS_FAINT_* target classes, including:

• No longer setting any of the MWS_FAINT target bits.
• No longer exempting MWS_FAINT from forced ledger TIMESTAMPs. There's no need to anymore.
• Removing special logic that had been added to merge MWS_FAINT with secondary targets.

In the end, we decided that this was the simplest way to make progress because we were in a bind after not starting the Main Survey with the MWS_FAINT target classes. The problem was that if we included MWS_FAINT targets they would occasionally be merged with secondary targets that had previously matched a different target, which would update the behavior of fiberassign. If we attempted to prevent the MWS_FAINT targets from merging with secondary targets, we would produce duplicate targets with the same TARGETID, and TARGETID needs to be unique to track targets downstream of desitarget.

We will revisit the MWS_FAINT target classes as a pure secondary class during the summer shutdown.

I'll merge this as soon as tests pass as I'll need to tag new versions of the Main Survey targets.