Remove pointless trainer_... fields from creature_template

[FlagFlayer]

🍰 Pullrequest

• Apply and correct conditions to remaining trainer gossip menu options.

• Remove trainer_... fields from creature_template (except for trainer_id).

• Get rid of deprecated "msg" field in IsTrainerOf and CanInteractWithBattleMaster (ancient code that doesn't function)

How2Test

• Talk to a trainer. Trainer gossip menu shows up if the correct conditions are met.
• Use .learn all_trainer. It correctly teaches all available trainer spells.

Todo / Checklist

• None

[ratkosrb]

What happened with the Soothsaying fixes, did that implementation require these changes first?

[mserajnik]

What happened with the Soothsaying fixes, did that implementation require these changes first?

I think he just decided to split up the PR, see his comment here: #1705 (comment)

[FlagFlayer]

What happened with the Soothsaying fixes, did that implementation require these changes first?

They did not require this, but since this part of the fixes makes the trainer_spell column become completely empty I bundled these fixes with this change.

What I'm missing for the Soothsaying fixes is sniffs of the gossip submenus when going through the option "I would like to relearn my leatherworking focus", as well as the correct order of entries when talking to Book Soothsaying for Dummies and having both the leatherworking and the engineering options available. I haven't been able to get around to getting these sniffs, I hope someone else might be able to obtain them at some point.