Fixes for bazel build with incompatible_autoload_externally set to empty

[shameekganguly]

🦟 Bug fix

Summary

When adding gz-msgs to BCR, I discovered that BCR presubmits on bazel 8 run with --incompatible_autoload_externally= by default. For context, that flag denotes a deprecation of native bazel support of language specific rules such as cc_binary and py_binary in bazel 8 to external rules from respective rules_xxx repositories (in bazel 9, the feature will be enforced by default).

This change fixes the few missing loads I discovered with

$ USE_BAZEL_VERSION=8.2.1 bazel build --incompatible_autoload_externally= ...

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
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