feat: add tool for visualizing compressed (and uncompressed) models (#3099)

Add a development tool that prints compressed and uncompressed
.tflite models to stdout in a human-readable, searchable,
structured, text format. Helpful annotations (indexes of lists,
names of operators, etc.) derived from the model are added as
virtual fields with names beginning with an _underscore.

Add a unit test which simply ensures the viewer does not crash
when run on several models found in the source tree.

BUG=see description

Author: rkuester

tensorflow/lite/micro/compression/BUILD

@@ -10,6 +10,7 @@ load(
 )
 load("@rules_python//python:defs.bzl", "py_binary", "py_library", "py_test")
 load("@tflm_pip_deps//:requirements.bzl", "requirement")
+load("view_tests.bzl", "generate_view_tests")
 
 package(
     default_visibility = [
@@ -229,3 +230,24 @@ py_test(
         requirement("tensorflow"),
     ],
 )
+
+py_binary(
+    name = "view",
+    srcs = [
+        "view.py",
+    ],
+    deps = [
+        ":metadata_py",
+        "//tensorflow/lite/python:schema_py",
+        "@absl_py//absl:app",
+        requirement("bitarray"),
+        requirement("prettyprinter"),
+    ],
+)
+
+generate_view_tests([
+    "//tensorflow/lite/micro/models:keyword_scrambled.tflite",
+    "//tensorflow/lite/micro/models:keyword_scrambled_8bit.tflite",
+    "//tensorflow/lite/micro/models:person_detect.tflite",
+    "//tensorflow/lite/micro/models:person_detect_vela.tflite",
+])