Remove the JS host generator

This commit removes the JS host generator from this repository as it now
lives at bytecodealliance/js-component-tools. The runtime tests will be
updated in a subsequent commit to use Wasmtime as a host for executing
components.

This additionally removes the demo as it's no longer possible to build
it in just this repository. The demo has slowly been getting less useful
over time as generators are removed from this repository. Additionally
it's always been a demo and not much more so it's more-or-less served
its purpose and doesn't seem to have a great place to fit any more. This
can possibly exist out-of-tree eventually in a separate location that
pulls together all known generators, but until that time it seems best
to just remove it for now.

Closes bytecodealliance#395

.github/workflows/main.yml

@@ -48,15 +48,11 @@ jobs:
     - uses: actions/setup-node@v2
       with:
         node-version: '16'
-    - name: Install NPM packages
-      run: npm install
-      working-directory: crates/gen-host-js
     - uses: actions/setup-java@v3
       with:
         java-version: '18'
         distribution: 'adopt'
     - run: cargo test --workspace
-    - run: cargo test -p wit-bindgen-gen-host-js --test runtime --features runtime-tests
 
   rustfmt:
     name: Rustfmt
@@ -67,36 +63,3 @@ jobs:
       run: rustup update stable && rustup default stable && rustup component add rustfmt
     - name: Format source code
       run: cargo fmt -- --check
-
-  demo:
-    name: Build wit-bindgen demo
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/checkout@v2
-    - run: rustup update stable --no-self-update && rustup default stable
-    - run: rustup target add wasm32-unknown-unknown
-    - run: npm install
-      working-directory: crates/wit-bindgen-demo
-
-    # Install the `wasm-tools` binary with the `component` subcommand that is all
-    # that's needed here.
-    - uses: actions/cache@v3
-      with:
-        path: ${{ runner.tool_cache }}/wasm-tools
-        key: wasm-tools-bin-1.0.17-${{ runner.os }}
-    - run: echo '${{ runner.tool_cache }}/wasm-tools/bin' >> $GITHUB_PATH
-    - run: |
-        cargo install \
-          wasm-tools@1.0.17 \
-          --root '${{ runner.tool_cache }}/wasm-tools' \
-          --locked \
-          --no-default-features \
-          --features component
-
-    - run: ./crates/wit-bindgen-demo/build.sh
-    - uses: JamesIves/github-pages-deploy-action@4.1.4
-      with:
-        branch: gh-pages
-        folder: static
-        single-commit: true
-      if: github.event_name == 'push' && github.ref == 'refs/heads/main'