"Smart" Abandoned Mineshaft Generation

Abandoned Mineshafts have already received multiple upgrades in the 1.17 snapshots to accommodate for much larger caves.  Now, mineshafts can generate with support pillars and chains holding them up for realsim.  However, more optimizations are necessary to prevent mineshafts from generating as messes of exposed wood floating in the middle of large caverns.  For this reason, I suggest a "smart" mineshaft bridge generation system is implemented.

1. Currently, mineshaft bridges generate with log pillars if they are closer to the ground than the ceiling.  However, when mineshaft bridges generate in the middle of thin, 40-block deep canyons, this can result in 20-block tall pillars spawning in a very thin space that looks very bad.  To prevent this, if a mineshaft bridge is shorter in length than the distance to the floor, pillars will NEVER generate.

2. Mineshafts can become very cluttered when a bridge in a large cave splits in many directions.  For this reason, bridges (shafts that are surrounded by air) cannot contain any intersections.

3. Two or more mineshaft bridges on top of each other can look cluttered and redundant.    For this reason, if a support pillar or chain hangs/supports on another part of a mineshaft, the bridge does not generate.

4. Bridges cannot be more than 20 blocks long and must reach the other side of the cave (cannot end in middair).

These four optimizations will make mineshafts appear cleaner and more realistic when they interact with large caves.