Switch to a batch IMU message

We only send in batches.  We would also like to forward these messages
across the network to the logger.  The resulting 2000 hz wakeups are
swamping message_gateway, and it isn't worth adding a batch forwarding
mode yet.

Change-Id: I2c2f5bc021a660e932e086965e10bc92f27e2ec1
diff --git a/frc971/wpilib/BUILD b/frc971/wpilib/BUILD
index bcdd2ce..734a231 100644
--- a/frc971/wpilib/BUILD
+++ b/frc971/wpilib/BUILD
@@ -267,6 +267,17 @@
     gen_reflections = 1,
 )
 
+flatbuffer_cc_library(
+    name = "imu_batch_fbs",
+    srcs = [
+        "imu_batch.fbs",
+    ],
+    gen_reflections = 1,
+    includes = [
+        ":imu_fbs_includes",
+    ],
+)
+
 cc_library(
     name = "ADIS16470",
     srcs = [
@@ -278,7 +289,9 @@
     restricted_to = ["//tools:roborio"],
     deps = [
         ":fpga_time_conversion",
+        ":imu_batch_fbs",
         ":imu_fbs",
+        "//aos/containers:sized_array",
         "//aos/events:event_loop",
         "//aos/time",
         "//third_party:wpilib",