Update test directives for `wasm32-wasip1`

* The WASI targets deal with the `main` symbol a bit differently than
  native so some `codegen` and `assembly` tests have been ignored.
* All `ignore-emscripten` directives have been updated to
  `ignore-wasm32` to be more clear that all wasm targets are ignored and
  it's not just Emscripten.
* Most `ignore-wasm32-bare` directives are now gone.
* Some ignore directives for wasm were switched to `needs-unwind`
  instead.
* Many `ignore-wasm32*` directives are removed as the tests work with
  WASI as opposed to `wasm32-unknown-unknown`.