Convert EMotionFX runtime uint32 -> size_t

This allows the EMotionFX runtime to compile with `/we4267` enabled, which
emits a warning when converting from `size_t` to a smaller type. All tests
for the runtime have been updated accordingly, and they pass.

In instances where a range-for loop could be used, or a std algorithm, that
was used instead of using `size_t numItems = vec.size()` and a for loop.

Casts to `uint32` were removed where possible. Some places remain, like in
the file formats.

Signed-off-by: Chris Burel <burelc@amazon.com>

Gems/EMotionFX/Code/Tests/SimulatedObjectSerializeTests.cpp

@@ -35,7 +35,7 @@ namespace EMotionFX
             size_t skeletonJointIndex;
             const Node* skeletonJoint = skeleton->FindNodeAndIndexByName(name, skeletonJointIndex);
             ASSERT_NE(skeletonJoint, nullptr);
-            ASSERT_NE(skeletonJointIndex, MCORE_INVALIDINDEX32);
+            ASSERT_NE(skeletonJointIndex, InvalidIndex);
 
             SimulatedJoint* simulatedJoint = object->AddSimulatedJoint(skeletonJointIndex);
             simulatedJoint->SetDamping(0.1f);