Update transition support (#847)

This completely updates the `transition_support.bzl` file. It now
essentially is a copy of the one in here:
https://github.com/bazelbuild/rules_apple/blob/f37305163dd7546f87839f3187e153c955cd20d8/apple/internal/transition_support.bzl

This is important as Bazel 7 has changed this a lot.

Changes:

- Delete old transition_support.bzl
- Add rules_apple transition_support.bzl
- Add rules_ios specific patches to transition_support.bzl (see the
`PATCH:` comments)
- Update existing rules to support this new transition_support
- Remove unused transitions from transition_support.bzl that are used in
rules_apple but not in rules_ios

docs/transition_support_doc.md

@@ -2,6 +2,22 @@
 
 Starlark transition support for Apple rules.
 
+This module makes the following distinctions around Apple CPU-adjacent values for clarity, based in
+part on the language used for XCFramework library identifiers:
+
+- `architecture`s or "arch"s represent the type of binary slice ("arm64", "x86_64").
+
+- `environment`s represent a platform variant ("device", "sim"). These sometimes appear in the "cpu"
+    keys out of necessity to distinguish new "cpu"s from an existing Apple "cpu" when a new
+    Crosstool-provided toolchain is established.
+
+- `platform_type`s represent the Apple OS being built for ("ios", "macos", "tvos", "visionos",
+    "watchos").
+
+- `cpu`s are keys to match a Crosstool-provided toolchain ("ios_sim_arm64", "ios_x86_64").
+    Essentially it is a raw key that implicitly references the other three values for the purpose of
+    getting the right Apple toolchain to build outputs with from the Apple Crosstool.
+
 <a id="transition_support.current_apple_platform"></a>
 
 ## transition_support.current_apple_platform

rules/BUILD.bazel

@@ -23,6 +23,7 @@ bzl_library(
     visibility = ["//visibility:public"],
     deps = [
         "@build_bazel_apple_support//configs:platforms",
+        "@build_bazel_rules_apple//apple",
     ],
 )
 

rules/force_load_direct_deps.bzl

@@ -33,7 +33,7 @@ force_load_direct_deps = rule(
     implementation = _impl,
     attrs = {
         "deps": attr.label_list(
-            cfg = transition_support.split_transition,
+            cfg = transition_support.apple_platform_split_transition,
             mandatory = True,
             doc =
                 "Deps",

rules/framework.bzl

@@ -1094,23 +1094,23 @@ apple_framework_packaging = rule(
         ),
         "deps": attr.label_list(
             mandatory = True,
-            cfg = transition_support.split_transition,
+            cfg = transition_support.apple_platform_split_transition,
             aspects = [apple_resource_aspect],
             doc =
                 """Objc or Swift rules to be packed by the framework rule
 """,
         ),
         "private_deps": attr.label_list(
             mandatory = False,
-            cfg = transition_support.split_transition,
+            cfg = transition_support.apple_platform_split_transition,
             aspects = [apple_resource_aspect],
             doc =
                 """Objc or Swift private rules to be packed by the framework rule
 """,
         ),
         "data": attr.label_list(
             mandatory = False,
-            cfg = transition_support.split_transition,
+            cfg = transition_support.apple_platform_split_transition,
             allow_files = True,
             doc =
                 """Objc or Swift rules to be packed by the framework rule
@@ -1132,15 +1132,15 @@ The default behavior bakes this into the top level app. When false, it's statica
         ),
         "vfs": attr.label_list(
             mandatory = False,
-            cfg = transition_support.split_transition,
+            cfg = transition_support.apple_platform_split_transition,
             doc =
                 """Additional VFS for the framework to export
 """,
         ),
         "transitive_deps": attr.label_list(
             aspects = [swift_clang_module_aspect],
             mandatory = True,
-            cfg = transition_support.split_transition,
+            cfg = transition_support.apple_platform_split_transition,
             doc =
                 """Deps of the deps
 """,
@@ -1185,7 +1185,7 @@ A list of framework targets (see
 [`ios_framework`](https://github.com/bazelbuild/rules_apple/blob/master/doc/rules-ios.md#ios_framework))
 that this target depends on.
 """,
-            cfg = transition_support.split_transition,
+            cfg = transition_support.apple_platform_split_transition,
         ),
         "_headermap_builder": attr.label(
             executable = True,
@@ -1204,7 +1204,7 @@ that this target depends on.
             """,
         ),
         "_child_configuration_dummy": attr.label(
-            cfg = transition_support.split_transition,
+            cfg = transition_support.apple_platform_split_transition,
             providers = [cc_common.CcToolchainInfo, ApplePlatformInfo],
             default = Label("@build_bazel_rules_apple//apple:default_cc_toolchain_forwarder"),
         ),

rules/internal/framework_middleman.bzl

@@ -122,7 +122,7 @@ framework_middleman = rule(
     implementation = _framework_middleman,
     attrs = {
         "framework_deps": attr.label_list(
-            cfg = transition_support.split_transition,
+            cfg = transition_support.apple_platform_split_transition,
             mandatory = True,
             doc =
                 """Deps that may contain frameworks
@@ -260,7 +260,7 @@ dep_middleman = rule(
     implementation = _dep_middleman,
     attrs = {
         "deps": attr.label_list(
-            cfg = transition_support.split_transition,
+            cfg = transition_support.apple_platform_split_transition,
             mandatory = True,
             doc =
                 """Deps that may contain frameworks