[spirv-reader] Split arithmetic, bit tests

Separate them into different test files, to match SPIR-V spec sections

Bug: tint:3
Change-Id: I89fe76230740da060d57ac23870069a5483b2d7d
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/20043
Reviewed-by: dan sinclair <dsinclair@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index c79492c..299e340 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -511,6 +511,7 @@
     "src/reader/spirv/enum_converter_test.cc",
     "src/reader/spirv/fail_stream_test.cc",
     "src/reader/spirv/function_arithmetic_test.cc",
+    "src/reader/spirv/function_bit_test.cc",
     "src/reader/spirv/function_cfg_test.cc",
     "src/reader/spirv/function_conversion_test.cc",
     "src/reader/spirv/function_decl_test.cc",