Copies priv/bootstrap to the root of the release and makes it executable.

This is the entrypoint Lambda invokes for a provided.al2023 function.

Renders our own vm.args/env.sh/remote.vm.args over Mix's generated defaults.

Called as a step (after :assemble), so :aws_lambda_runtime is guaranteed to be compiled and loaded by the time Application.app_dir/2 resolves its priv dir — unlike a rel_templates_path release option, which would need to be computed inside mix.exs's project/0, before Mix has fetched or compiled any dependency.