Update flags documentation:

- new ammo effect flags.
- alternative body part names (left / right body part)
- removed techniques, completely jsonized
- diesel

Fixes #9973

> it looks like it's also intended to work this way on monsters (specifically, the Nether monsters that melt away should never gib).

The flag for monsters is called "NO_GIBS", it is documented in JSON_FLAGS.md and it works fine.

However they could probably change to a common string, what should it be:
- `NO_GIBS`
- `NO_GIB`
- `NOGIB`
- `NOGIBS`

Also the list of ammo types should probably be removed from this file. Ammo types are defined in json completely, listing them here is just pointless and likely outdated redundancy.