replace rbe_autoconfig with rbe_configs_gen

The `rbe_autoconfig` workspace rule [is being deprecated](java/com/engflow/eventstore/storage/InvocationStreamHandler.java) in favor of checking in the output of the [`rbe_configs_gen` tool](https://github.com/bazelbuild/bazel-toolchains#rbe_configs_gen---cli-tool-to-generate-configs).