Split //frc971/zeroing into multiple files

It's still a single target, and one massive header file. We should
actually split that up in a future refactoring. However, this does make
it easier to find the relevant parts within each file.

Change-Id: I7abc26f2e3d88da4558f54d56e6db4233cc4c30f
diff --git a/frc971/zeroing/BUILD b/frc971/zeroing/BUILD
index 75d610a..5955f8b 100644
--- a/frc971/zeroing/BUILD
+++ b/frc971/zeroing/BUILD
@@ -59,9 +59,18 @@
 cc_library(
     name = "zeroing",
     srcs = [
-        "zeroing.cc",
+        "absolute_encoder.cc",
+        "hall_effect_and_position.cc",
+        "pot_and_absolute_encoder.cc",
+        "pot_and_index.cc",
+        "pulse_index.cc",
     ],
     hdrs = [
+        "absolute_encoder.h",
+        "hall_effect_and_position.h",
+        "pot_and_absolute_encoder.h",
+        "pot_and_index.h",
+        "pulse_index.h",
         "zeroing.h",
     ],
     deps = [
@@ -76,11 +85,16 @@
 cc_test(
     name = "zeroing_test",
     srcs = [
-        "zeroing_test.cc",
+        "absolute_encoder_test.cc",
+        "hall_effect_and_position_test.cc",
+        "pot_and_absolute_encoder_test.cc",
+        "pot_and_index_test.cc",
+        "pulse_index_test.cc",
+        "relative_encoder_test.cc",
+        "zeroing_test.h",
     ],
     deps = [
         ":zeroing",
-        "//aos:die",
         "//aos/testing:googletest",
         "//aos/testing:test_shm",
         "//frc971/control_loops:control_loops_fbs",