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/AnimGraphSyncTrackTests.cpp

@@ -95,8 +95,8 @@ namespace EMotionFX
             {
                 MakeNoEvents,
                 0.5f,
-                MCORE_INVALIDINDEX32,
-                MCORE_INVALIDINDEX32
+                InvalidIndex,
+                InvalidIndex
             },
             {
                 MakeOneEvent,
@@ -267,8 +267,8 @@ namespace EMotionFX
                 0,     // startingIndex
                 0,     // inEventAIndex
                 1,     // inEventBIndex
-                MCORE_INVALIDINDEX32, // expectedEventA
-                MCORE_INVALIDINDEX32, // expectedEventB
+                InvalidIndex, // expectedEventA
+                InvalidIndex, // expectedEventB
                 false, // mirrorInput
                 false, // mirrorOutput
                 true   // forward