Switch everything to platforms

This patch switches the codebase over from using the "cpu"
mechanism to using bazel platforms. See
https://docs.bazel.build/versions/master/platforms.html for some more
information.

Most of the substantial changes are in //tools. Instead of using
`cc_toolchain_suite` rules, we now use regular `toolchain` rules that
are registered in the WORKSPACE. That also means that bazel now uses
the target platform to select the compiler.

All --cpu=* arguments should now be --config=* arguments. For example,
`--cpu=roborio` should now be `--config=roborio`. The CI script and
all documentation has been updated to reflect that.

The remainder of the changes revolve around tagging all targets with
`target_compatible_with`.  The old mechanism allowed us to specify
repo-wide defaults. The new mechanism does not. That means every
target that didn't have any compatibility specified, now requires
compatibility with `@platforms//os:linux`.

I used buildozer for the vast majority of `target_compatible_with`
changes. buildozer automatically buildifies any BUILD files it
touches. That means this patch also contains a few non-functional
changes that I was too lazy to remove.

Change-Id: I66d6e6ad9161520ee397597cdb492585820a3acd
diff --git a/aos/vision/blob/BUILD b/aos/vision/blob/BUILD
index e025ed3..2efd99e 100644
--- a/aos/vision/blob/BUILD
+++ b/aos/vision/blob/BUILD
@@ -1,4 +1,5 @@
-load("//tools/build_rules:gtk_dependent.bzl", "gtk_dependent_cc_binary", "gtk_dependent_cc_library")
+load("//tools:platforms.bzl", "platforms")
+load("//tools/build_rules:gtk_dependent.bzl", "gtk_dependent_cc_library")
 
 package(default_visibility = ["//visibility:public"])
 
@@ -6,6 +7,7 @@
     name = "range_image",
     srcs = ["range_image.cc"],
     hdrs = ["range_image.h"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         "//aos/vision/debug:overlay",
         "//aos/vision/image:image_types",
@@ -18,12 +20,14 @@
 cc_library(
     name = "region_alloc",
     hdrs = ["region_alloc.h"],
+    target_compatible_with = ["@platforms//os:linux"],
 )
 
 cc_library(
     name = "contour",
     srcs = ["contour.cc"],
     hdrs = ["contour.h"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":range_image",
         ":region_alloc",
@@ -40,6 +44,7 @@
     hdrs = [
         "threshold.h",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":range_image",
         "//aos/logging",
@@ -52,6 +57,7 @@
     srcs = [
         "threshold_test.cc",
     ],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":range_image",
         ":threshold",
@@ -64,10 +70,10 @@
     name = "hierarchical_contour_merge",
     srcs = ["hierarchical_contour_merge.cc"],
     hdrs = ["hierarchical_contour_merge.h"],
-    restricted_to = [
-        "//tools:k8",
-        "//tools:armhf-debian",
-    ],
+    target_compatible_with = platforms.any_of([
+        "@platforms//cpu:x86_64",
+        "//tools/platforms/hardware:raspberry_pi",
+    ]),
     deps = [
         ":contour",
         ":disjoint_set",
@@ -79,12 +85,14 @@
 cc_library(
     name = "disjoint_set",
     hdrs = ["disjoint_set.h"],
+    target_compatible_with = ["@platforms//os:linux"],
 )
 
 cc_library(
     name = "find_blob",
     srcs = ["find_blob.cc"],
     hdrs = ["find_blob.h"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":disjoint_set",
         ":range_image",
@@ -98,6 +106,7 @@
     name = "codec",
     srcs = ["codec.cc"],
     hdrs = ["codec.h"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":range_image",
         "//aos/vision/debug:overlay",
@@ -109,6 +118,7 @@
 cc_test(
     name = "codec_test",
     srcs = ["codec_test.cc"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":codec",
         "//aos/testing:googletest",
@@ -119,6 +129,7 @@
     name = "move_scale",
     srcs = ["move_scale.cc"],
     hdrs = ["move_scale.h"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":range_image",
         "//aos/vision/image:image_types",
@@ -129,6 +140,7 @@
     name = "test_utils",
     srcs = ["test_utils.cc"],
     hdrs = ["test_utils.h"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":range_image",
     ],
@@ -138,6 +150,7 @@
     name = "transpose",
     srcs = ["transpose.cc"],
     hdrs = ["transpose.h"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":range_image",
     ],
@@ -146,6 +159,7 @@
 cc_test(
     name = "transpose_test",
     srcs = ["transpose_test.cc"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":test_utils",
         ":transpose",
@@ -156,6 +170,7 @@
 gtk_dependent_cc_library(
     name = "stream_view",
     hdrs = ["stream_view.h"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":range_image",
         "//aos/vision/debug:debug_window",