Certain player animation controllers stopped working in 1.15

Please ignore this ticket, the issue is described better in MCM-975

Partner Rank: 1

Verification builds: 1.15.0.54
Regression builds: 1.14.0.30

Summary: Certain player animation controllers are not working in 1.15. Unfortunately, my testing was unable to determine exactly what the criteria are, but I have a repro world.

Impact: This makes two upcoming, finished maps entirely unplayable in 1.15, despite working fine in 1.14.

Repro Steps:

1. Download the world from slack
2. Hold the spawn egg item in your hand

Expected Results: Holding the item puts you in survival mode

Observed Results: Stay in adventure mode, unable to progress

Screenshots/Videos attached: No

Notes: The broken player animation controller here is player_tool.json. Note that player_punch.json works fine even in 1.15.