Bring LimitNOFILE back down to 1024 * 1024 due to the performance impact of too many FDs

[grahamc]

…ct of too many FDs

Description

Checklist

• Formatted with cargo fmt
• Built with nix build
• Ran flake checks with nix flake check
• Added or updated relevant tests (leave unchecked if not applicable)
• Added or updated relevant documentation (leave unchecked if not applicable)
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