chore: enable exec tools toolchain by default

Author: rickeylev

CHANGELOG.md

@@ -35,6 +35,9 @@ A brief description of the categories of changes:
   (or equivalent).
 * (toolchains) `py_runtime.implementation_name` now defaults to `cpython`
   (previously it defaulted to None).
+* (toolchains) The exec tools toolchain is enabled by default. It can be
+  disabled by setting
+  {obj}`--@rules_python//python/config_settings:exec_tools_toolchain=disabled`.
 * (deps) stardoc 0.6.2 added as dependency.
 
 ### Fixed

python/config_settings/BUILD.bazel

@@ -42,7 +42,7 @@ string_flag(
 
 string_flag(
     name = "exec_tools_toolchain",
-    build_setting_default = ExecToolsToolchainFlag.DISABLED,
+    build_setting_default = ExecToolsToolchainFlag.ENABLED,
     values = sorted(ExecToolsToolchainFlag.__members__.values()),
     # NOTE: Only public because it is used in py_toolchain_suite from toolchain
     # repositories