Remove the .NET implementation. (#1477)

This commit removes the .NET implementation from Wasmtime.

It now exists at https://github.com/bytecodealliance/wasmtime-dotnet.

Also updates the Wasmtime book to include information about using Wasmtime from
.NET.

.github/workflows/main.yml

@@ -334,52 +334,6 @@ jobs:
         name: bins-${{ matrix.os }}
         path: dist
 
-  # Build and test the .NET bindings
-  dotnet:
-    name: Test Wasmtime for .NET bindings
-    runs-on: ${{ matrix.os }}
-    strategy:
-      matrix:
-        build: [linux-debug, linux-release, macos-debug, macos-release, windows-debug, windows-release]
-        include:
-          - build: linux-debug
-            os: ubuntu-latest
-            config: debug
-          - build: linux-release
-            os: ubuntu-latest
-            config: release
-          - build: macos-debug
-            os: macos-latest
-            config: debug
-          - build: macos-release
-            os: macos-latest
-            config: release
-          - build: windows-debug
-            os: windows-latest
-            config: debug
-          - build: windows-release
-            os: windows-latest
-            config: release
-    steps:
-    - uses: actions/checkout@v1
-      with:
-        submodules: true
-    - uses: ./.github/actions/install-rust
-    - uses: ./.github/actions/binary-compatible-builds
-    - run: rustup target add wasm32-wasi
-    - uses: actions/setup-dotnet@v1
-      with:
-        dotnet-version: '3.0.101'
-    - name: Test
-      run: |
-        cd crates/misc/dotnet/tests
-        dotnet test -c ${{ matrix.config }}
-    - name: Create package
-      run: |
-        cd crates/misc/dotnet/src
-        dotnet pack -c ${{ matrix.config }}
-      if: matrix.os == 'macos-latest' # Currently the pack target only supports macOS
-
   # Consumes all published artifacts from all the previous build steps, creates
   # a bunch of tarballs for all of them, and then publishes the tarballs
   # themselves as an artifact (for inspection) and then optionally creates