Damage sources converted to entity damage sources have caused death messages to become unused

Note: Since 23w06a, these death messages are no longer technically unused, since you can obtain them by using the new /damage command. I am not sure whether this ticket should still be considered valid though.

A lot of entity damage sources have not always been entity damage sources, since they were once environmental damage sources. This caused their ".player" death message variants to become unused, but their translation strings still exist.

Affected death messages:

• death.attack.sting.player (well, this one was always unused, so it doesn't have the same history as the rest)

• death.attack.fireworks.player

• death.attack.sonic_boom.player

• death.attack.anvil.player

• death.attack.fallingBlock.player

• death.attack.fallingStalactite.player

How to reproduce:

1. Execute the following command, replacing <message> with one of the above strings:

   /tellraw @s {"translate":"<message>"}

   → ❌ The message that appears is translated.

Expected result:

Previously existing death messages that were removed due to their damage sources being changed from environmental to entity damage would display as raw translation strings.

Observed result:

The death messages listed above are still translated.