Rename native.rule and native.rules to {existing_rule,existing_rules}
Rename native.rule and native.rules to {existing_rule,existing_rules}

This is to avoid confusion between rule(), which declares a new build
rules, and native.rule(), which can only be used in macros to inspect
the BUILD file processed so far.

native.{rule,rules} is maintained and marked deprecated to smooth the
transition for early adopters.

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MOS_MIGRATED_REVID=113250194

davidzchen/bazel-website,davidzchen/bazel-website,bazelbuild/bazel-website,davidzchen/bazel-website,davidzchen/bazel-website,bazelbuild/bazel-website,bazelbuild/bazel-website