Chat reports cannot be sent if combined size of reported messages and contextual messages is too large

The bug

Chat reports cannot be sent ("Request payload too big") when the sum of the sizes of the reported messages and their contextual messages is too large.

This can be used by a player to prevent a malicious message from being reported by someone else.

One would expect messages to be trimmed in the request to ensure the report can be sent.

How to reproduce

1. Create a new default world, and open the world to LAN
2. Run the command:

   /execute as @e[type=!player,limit=1] run say A bug?

3. Run the command:

   /say @e @e @e @e @e @e @e @e @e @e @e @e @e @e @e @e @e @e @e @e @e

4. Open the Social Interactions menu, and start a chat report for the entity that said "A bug?" (MC-253497)
5. Select their message, select a report category, and submit the report
   Report fails to be sent because of the large contextual message ("Request payload too big")