Enable Android Platforms by default for Android-related builds

Fixes bazelbuild#16285.

RELNOTES: Enable Platforms and Toolchains for Android. Android projects will need to stop passing the legacy flag `--fat_apk_cpu`, and instead use `--android_platforms` using platforms defined with the `@platforms//os:android` constraint. The https://github.com/bazelbuild/rules_android repository defines four standard Android platforms for projects that use those rules, `@rules_android//:armeabi-v7a`, `@rules_android//:arm64-v8a`, `@rules_android//:x86`, `@rules_android//:x86_64`.

Blog post describing these changes to follow.

Closes bazelbuild#19726.

PiperOrigin-RevId: 574153852
Change-Id: Ief1e1be95fa03dd038a912dd318628ffdd562eaa

src/main/java/com/google/devtools/build/lib/rules/android/AndroidConfiguration.java

@@ -775,7 +775,7 @@ public static class Options extends FragmentOptions {
 
     @Option(
         name = "incompatible_enable_android_toolchain_resolution",
-        defaultValue = "false",
+        defaultValue = "true",
         documentationCategory = OptionDocumentationCategory.TOOLCHAIN,
         effectTags = {OptionEffectTag.LOADING_AND_ANALYSIS},
         metadataTags = {OptionMetadataTag.INCOMPATIBLE_CHANGE},