Enable Python tests, standardise variable spelling and fix arg checking (#1533)

I found these with a quick find-and-replace and checked against the inbuilt Python type checking. I am away from my robot and can't really
confirm there are no flow-on effects. There are no other active usages of the bad casing in the Python code, so we should be good. The generated serde messages already use this casing, so we don't need to update there.

photon-lib/py/photonlibpy/photonPoseEstimator.py

@@ -269,8 +269,8 @@ class PhotonPoseEstimator:
     def _multiTagOnCoprocStrategy(
         self, result: PhotonPipelineResult
     ) -> Optional[EstimatedRobotPose]:
-        if result.multiTagResult.estimatedPose.isPresent:
-            best_tf = result.multiTagResult.estimatedPose.best
+        if result.multitagResult is not None:
+            best_tf = result.multitagResult.estimatedPose.best
             best = (
                 Pose3d()
                 .transformBy(best_tf)  # field-to-camera

photon-lib/py/photonlibpy/targeting/multiTargetPNPResult.py

@@ -8,8 +8,8 @@ class PnpResult:
     best: Transform3d = field(default_factory=Transform3d)
     alt: Transform3d = field(default_factory=Transform3d)
     ambiguity: float = 0.0
-    bestReprojError: float = 0.0
-    altReprojError: float = 0.0
+    bestReprojErr: float = 0.0
+    altReprojErr: float = 0.0
 
     photonStruct: "PNPResultSerde" = None
 

photon-lib/py/photonlibpy/targeting/photonPipelineResult.py

@@ -29,7 +29,7 @@ class PhotonPipelineResult:
     # Python users beware! We don't currently run a Time Sync Server, so these timestamps are in
     # an arbitrary timebase. This is not true in C++ or Java.
     metadata: PhotonPipelineMetadata = field(default_factory=PhotonPipelineMetadata)
-    multiTagResult: Optional[MultiTargetPNPResult] = None
+    multitagResult: Optional[MultiTargetPNPResult] = None
 
     def getLatencyMillis(self) -> float:
         return (