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/y2014/control_loops/python/BUILD b/y2014/control_loops/python/BUILD
index cba8cea..60488b4 100644
--- a/y2014/control_loops/python/BUILD
+++ b/y2014/control_loops/python/BUILD
@@ -6,7 +6,7 @@
         "drivetrain.py",
     ],
     legacy_create_init = False,
-    restricted_to = ["//tools:k8"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":python_init",
         "//external:python-gflags",
@@ -22,7 +22,7 @@
         "polydrivetrain.py",
     ],
     legacy_create_init = False,
-    restricted_to = ["//tools:k8"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":python_init",
         "//external:python-gflags",
@@ -37,7 +37,7 @@
         "drivetrain.py",
         "polydrivetrain.py",
     ],
-    restricted_to = ["//tools:k8"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         "//external:python-gflags",
         "//external:python-glog",
@@ -53,7 +53,7 @@
         "claw.py",
     ],
     legacy_create_init = False,
-    restricted_to = ["//tools:k8"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":polydrivetrain_lib",
         ":python_init",
@@ -70,7 +70,7 @@
         "shooter.py",
     ],
     legacy_create_init = False,
-    restricted_to = ["//tools:k8"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":python_init",
         "//external:python-gflags",
@@ -86,7 +86,7 @@
         "extended_lqr.py",
     ],
     legacy_create_init = False,
-    restricted_to = ["//tools:k8"],
+    target_compatible_with = ["@platforms//os:linux"],
     deps = [
         ":python_init",
         "//external:python-gflags",
@@ -99,6 +99,7 @@
 py_library(
     name = "python_init",
     srcs = ["__init__.py"],
+    target_compatible_with = ["@platforms//os:linux"],
     visibility = ["//visibility:public"],
     deps = ["//y2014/control_loops:python_init"],
 )