Add separate step to GHA workflow for rust doc

[DieracDelta]

This PR closes #115 and:

• Bumps the rust version in flake.lock
• Adds a separate step for cargo doc so we can view warnings
• Increases the aggressiveness of the cargo doc invocation. Now it generates private documentation for all workspace members and all examples
• Fixes some of the encountered warnings

Note that if this check fails locally, it may be a rust stable. Rust stable needs to be at least 1.60.0 which came out very recently (<1 hour at the time of posting). Fenix hasn't run the workflow to generate a new stable toolchain yet.

[VictorKoenders]

I think it'd make sense for the documentation steps to be moved to .github/workflows/doc.yml or something

[DieracDelta]

I'm going to leave this open until we get access to rust 1.60.0 since this is needed for the workflow to pass

[VictorKoenders]

I think that we should switch this CI to a github runner for now:

From build_libp2p_networking.yml

      - name: Checkout Repository
        uses: actions/checkout@v3

      - name: Configure Git
        run: |
          git config --global url."https://ancient123:${{ secrets.ORG_GITHUB_PATH }}@github.com/".insteadOf git://github.com/
          git config --global url."https://ancient123:${{ secrets.ORG_GITHUB_PAT }}@github.com/".insteadOf ssh://git@github.com/
      - name: Install stable toolchain
        uses: actions-rs/toolchain@v1
        with:
          profile: default
          toolchain: stable
          override: true
          default: true
          components: rustfmt, clippy

      - name: Enable Rust Caching
        uses: Swatinem/rust-cache@v1

Should get rust 1.60