legacy burst is orphaned, needs to be phased out from mods

[RoyalFox2140]

Describe the bug

After #5734 burst is orphaned. It needs removal, but mods use it. It needs a period of warning messages to isolate the mods that still use it.

You can use fire modes instead, it's much better.

Steps To Reproduce

check the code

Screenshots

No response

Versions and configuration

All

Additional context

No response

[scarf005]

https://github.com/search?q=LANGUAGE%3Ajson+%2F"type"%3A+"GUN"(.|\n)*"burst"%3A%2F&type=code

there's lots of false positives (i.e DDA mods, DDA and BN forks) but looks like there's still some usage outside kenan's