Move all examples to a top-level directory (#1286)

* Move all examples to a top-level directory

This commit moves all API examples (Rust and C) to a top-level
`examples` directory. This is intended to make it more discoverable and
conventional as to where examples are located. Additionally all examples
are now available in both Rust and C to see how to execute the example
in the language you're familiar with. The intention is that as more
languages are supported we'd add more languages as examples here too.

Each example is also accompanied by either a `*.wat` file which is
parsed as input, or a Rust project in a `wasm` folder which is compiled
as input.

A simple driver crate was also added to `crates/misc` which executes all
the examples on CI, ensuring the C and Rust examples all execute
successfully.

.github/workflows/main.yml

@@ -184,9 +184,10 @@ jobs:
         Get-Command clang.exe
         clang.exe --version
 
-    # Install wasm32-wasi target in order to build wasi-common's integration
-    # tests
+    # Install wasm32 targets in order to build various tests throughout the
+    # repo
     - run: rustup target add wasm32-wasi
+    - run: rustup target add wasm32-unknown-unknown
 
     - run: cargo fetch --locked
     - run: cargo fetch --locked --manifest-path crates/test-programs/wasi-tests/Cargo.toml
@@ -197,6 +198,9 @@ jobs:
     - run: cargo build --manifest-path crates/api/Cargo.toml --features lightbeam
       if: matrix.rust == 'nightly'
 
+    # Ensure all our examples build and execute
+    - run: cargo run -p run-examples
+
     # Build and test all features except for lightbeam
     - run: cargo test --features test_programs --all --exclude lightbeam --exclude wasmtime-c-api -- --nocapture
       env:
@@ -205,7 +209,7 @@ jobs:
 
     # Test debug (DWARF) related functionality.
     - run: cargo test test_debug_dwarf_ -- --ignored --nocapture --test-threads 1
-      if: matrix.os == 'ubuntu-latest' 
+      if: matrix.os == 'ubuntu-latest'
       env:
         RUST_BACKTRACE: 1
         RUSTFLAGS: "-D warnings"