Clean up gas miners (#29657)

Separate the environment check from CapSpawnAmount into GetValidEnvironment to make the code a little cleaner, and also makes these two checks independent.

CapSpawnAmount and GetValidEnvironment now both have zero side-effects

Broken renamed Idle to reflect its use. Broken in my mind implies that there's some method for fixing.

---------

Co-authored-by: Partmedia <kevinz5000@gmail.com>

Resources/Prototypes/Entities/Structures/Piping/Atmospherics/miners.yml

@@ -66,8 +66,6 @@
   parent: GasMinerBase
   id: GasMinerNitrogen
   suffix: Shuttle, 300kPa
-  placement:
-    mode: SnapgridCenter
   components:
     - type: GasMiner
       spawnGas: Nitrogen
@@ -94,8 +92,6 @@
   name: CO2 gas miner
   parent: GasMinerBase
   id: GasMinerCarbonDioxide
-  placement:
-    mode: SnapgridCenter
   components:
     - type: GasMiner
       spawnGas: CarbonDioxide
@@ -104,8 +100,6 @@
   name: plasma gas miner
   parent: GasMinerBase
   id: GasMinerPlasma
-  placement:
-    mode: SnapgridCenter
   components:
     - type: GasMiner
       spawnGas: Plasma
@@ -114,8 +108,6 @@
   name: tritium gas miner
   parent: GasMinerBase
   id: GasMinerTritium
-  placement:
-    mode: SnapgridCenter
   components:
     - type: GasMiner
       spawnGas: Tritium
@@ -124,8 +116,6 @@
   name: water vapor gas miner
   parent: GasMinerBase
   id: GasMinerWaterVapor
-  placement:
-    mode: SnapgridCenter
   components:
     - type: GasMiner
       spawnGas: WaterVapor
@@ -134,8 +124,6 @@
   name: ammonia gas miner
   parent: GasMinerBase
   id: GasMinerAmmonia
-  placement:
-    mode: SnapgridCenter
   components:
     - type: GasMiner
       spawnGas: Ammonia
@@ -144,8 +132,6 @@
   name: nitrous oxide gas miner
   parent: GasMinerBase
   id: GasMinerNitrousOxide
-  placement:
-    mode: SnapgridCenter
   components:
     - type: GasMiner
       spawnGas: NitrousOxide