Reunify workspace; disable ring-compat doctests (#442)

Reverts the changes from #433 that split the `ed25519` crate out into
its own namespace.

Instead, temporarily disables the `ring-compat` dependency and doctests
in the `ed25519` crate until it's updated to the latest version of the
`signature` crate.

Fixes #440

.github/workflows/security-audit.yml

@@ -26,7 +26,3 @@ jobs:
       - uses: actions-rs/audit-check@v1
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
-      - uses: actions-rs/audit-check@v1
-        working-directory: ed25519
-        with:
-          token: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/workspace.yml

@@ -27,11 +27,6 @@ jobs:
         with:
           command: fmt
           args: --all -- --check
-      - uses: actions-rs/cargo@v1
-        working-directory: ed25519
-        with:
-          command: fmt
-          args: --all -- --check
 
   clippy:
     runs-on: ubuntu-latest
@@ -44,5 +39,3 @@ jobs:
           override: true
           profile: minimal
       - run: cargo clippy --all-features -- -D warnings
-      - run: cargo clippy --all-features -- -D warnings
-        working-directory: ed25519