This commit adds a test harness and the beginnings of a test suite for
the crate that performs GC over a wasm module. This crate historically
has had zero tests because it was thought that it would no longer be
used once LLD landed with `--gc-sections`, but `wasm-bindgen` has come
to rely more and more on `wasm-gc` for various purposes.
The last release of `wasm-bindgen` was also released with a bug in the
recently refactored support in the `wasm-gc` crate, providing a perfect
time and motivation to start writing some tests!
All tests added here are `*.wat` files which contain the expected output
after the gc pass is executed. Tests are automatically updated with
`BLESS_TESTS=1` in the environment, which is the expected way to
generate the output for each test.
This commit updates the `wasm-gc` pass of wasm-bindgen to eliminate
duplicate types in the type section, effectively enabling a gc of the
type section itself. The main purpose here is ensure that code generated
by `wasm-bindgen` itself doesn't have to go too far out of its way to
deduplicate at generation time, but rather it can rely on the gc pass to
clean up.
Note that this currently depends on paritytech/parity-wasm#231, but this
can be updated if that ends up not landing.
The `wasm-bindgen` crate is effectively the only user of this crate now
that the `wasm-gc` tool has been deprecated. It's also much easier to
keep it in this repository as it's easier to sync changes to
`parity-wasm`. I'd also like to start refactoring out utilities for
managing a `parity_wasm::Module` to share between this crate and the
other CLI support code.
