[maintenance] Bazel 9 & integration test maintenance

[agluszak]

Migrate examples and tests to support both bzlmod and workspace modes, update dependencies and Bazel to 9.0.0rc5, and add MODULE.bazel files for examples

[agluszak]

Seems to be blocked on bazelbuild/rules_android_ndk#119 ;_;

ERROR: package contains errors: : Traceback (most recent call last):
	File "/var/lib/buildkite-agent/.cache/bazel/_bazel_buildkite-agent/ec321eb2cc2d0f8f91b676b6d4c66c29/sandbox/linux-sandbox/797/execroot/_main/_tmp/5ba068ea4211ab3cdee54e123c907494/_bazel_buildkite-agent/36f1913b4bad55a69e352b3bbee55a27/external/rules_android_ndk++android_ndk_repository_extension+androidndk/BUILD.bazel", line 25, column 11, in <toplevel>
		cc_library(
	File "/virtual_builtins_bzl/bazel/exports.bzl", line 40, column 9, in _removed_rule_failure
Error in fail: 
         This rule has been removed from Bazel. Please add a `load()` statement for it.
         This can also be done automatically by running:
         buildifier --lint=fix <path-to-BUILD-or-bzl-file>
         
ERROR: /var/lib/buildkite-agent/.cache/bazel/_bazel_buildkite-agent/ec321eb2cc2d0f8f91b676b6d4c66c29/sandbox/linux-sandbox/797/execroot/_main/bazel-out/k8-fastbuild/bin/examples/android_bzlmod_.bazelversion_test.runfiles/_main/examples/android/app/BUILD.bazel:5:15: While resolving toolchains for target //app:app (c02f913): invalid registered toolchain '@androidndk//:all': Error evaluating '@androidndk//:all': error loading package '@@rules_android_ndk++android_ndk_repository_extension+androidndk//': Package '' contains errors

Looks like this rules_android_ndk dep wasn't necessary at all 🤷

[Bencodes]

Pinning this will help improve test perf a ton.