Additional documentation on reproducible builds

[heavypackets]

The PR adds deterministic build motivation and additional details on to the risczero build docs, including a link to install the Docker dependency on desktops.

This resolves #867.

[tzerrell]

Looks good up to one comment on the ELFs

[heavypackets]

Updated to reflect new risczero build output.

[github-actions]

Benchmark for Linux-cuda

    <details open>
      <summary>Click to hide benchmark</summary>
      Benchmarks have changed between the two branches, unable to diff.
    </details>

Benchmark for Linux-default

    <details open>
      <summary>Click to hide benchmark</summary>
      Benchmarks have changed between the two branches, unable to diff.
    </details>

Benchmark for macOS-default

    <details open>
      <summary>Click to hide benchmark</summary>
      Benchmarks have changed between the two branches, unable to diff.
    </details>

Benchmark for macOS-metal

    <details open>
      <summary>Click to hide benchmark</summary>
      Benchmarks have changed between the two branches, unable to diff.
    </details>