Tune down trapdoor spider spawns

[Venera3]

Summary

Bugfixes "Adjust trapdoor spider dens"

Purpose of change

Trapdoor spider dens spawn two dozen giant trapdoor spiders who make a mess of your lawn and/or eat Day1 survivors for breakfast. This gets them down to smalled bunches of small spawns (at least at first), with some gibs strewn around for good measure to warn you.

Describe the solution

Reduced and randomized the trapdoor trap spawns, changed the spawn range and the spawned monster to the small version of the spooders - since they evolve instead of growing up, they will get bigger with time.

Describe alternatives you've considered

Rework them properly, but doing ambush monsters right would need a lot of infra we don't really have, and would definitely take more time than what I want to spend for the moment. One of these days.

Testing

Spawned the map extra prior to the changes, got torn apart.
Spawned the map extra after the changes, saw some mounds and bug bits lying suspiciously around, got torn apart slightly less.

Additional context

Fixes #61017

[PatrikLundell]

It doesn't fix the problem, but it would reduce the consequences a bit. As mentioned, fixing it really would require a rework of ambush predators.

Is there a way to change the trap effect over time? As far as I understand the triggered trap would summon the small version regardless when it's triggered, while it really ought to summon small ones early on and larger ones later so it didn't matter whether the trap was triggered on day one and the spider remained in that position due to a lack of prey to pursue, or the trap was just triggered at the one year mark: you ideally would face the same type of spider in both cases.

[Venera3]

since they evolve instead of growing up, they will get bigger with time

The small spiders will roll to evolve on spawn, just like every other half_life mob.