Some tests fail because of RNG

[Coolthulhu]

When adding certain features, I altered some of the tests, but without enough precision, so they randomly fail.

• Throwing lethality test. This test is inherently RNG-dependent and doesn't need to be. But a quick fix could be to properly calculate the expected numbers - I only estimated them.
• Burst attack test - as above, but the de-RNG-ing would be a bit more complex.
• Final lab placement test - this one is the rarest, but also the hardest to fix. Would require redesigning lab generation to properly ensure the lab always exists and has proper form.
• NPC escaping dangerous terrain

[olanti-p]

Some player temperature test also started to fail, example from https://github.com/cataclysmbnteam/Cataclysm-BN/runs/7958233612 run on #1801

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cata_test is a Catch v2.13.8 host application.
Run with -? for options

Randomness seeded to: 1661192385

-------------------------------------------------------------------------------
Player body temperatures within expected bounds.
-------------------------------------------------------------------------------
player_test.cpp:284
...............................................................................

player_test.cpp:281: FAILED:
  REQUIRE( p.body_wetness == decltype( p.body_wetness )() )
with expansion:
  { 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 2, 2 }
  ==
  { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }

[olanti-p]

And vehicle split tests, example from https://github.com/cataclysmbnteam/Cataclysm-BN/runs/7932860706 run on #1793

-------------------------------------------------------------------------------
vehicle_split_section
-------------------------------------------------------------------------------
vehicle_split_test.cpp:13
...............................................................................

vehicle_split_test.cpp:30: FAILED:
  REQUIRE( veh_ptr != nullptr )
with expansion:
  nullptr != nullptr