These tests will build wasm test projects, as part of each test method,
and run them.

Other library tests are run with `xharness`, and the test assembly is run
under wasm.  But here we want to run them with xunit, outside wasm. So,
this has different requirements for the helix payload, eg, the sdk,
xunit console runner etc.

To make it work, a new Scenario - `BuildWasmApps` is added, which emits
it's archives in a `buildwasmapps/` folder, which makes it easy to pick
up for the helix test run.

The tests are added under `src/tests/BuildWasmApps/Wasm.Build.Tests`, but
they use `Directory.Build*` from `src/libraries`, similar to how
FunctionalTests do it.

Another use case of this kinda scenario are the wasm debugger tests,
in which the individual test methods launch wasm apps, and then debug
them. (TBD)

Tests:

- The initial set of tests are just proof-of-concept, and more will be
  added once this is merged.

Note: The individual tests build test projects, and then run them with
`xharness`, under `v8`, and Chrome.

This uses `mono-cil-strip` from a mono installation. And in it's current
form it can cause issues, so disabling it for now.

.. this allows supporting other properties from xunit*targets, eg. to
run a particular test `$(XUnitMethodName)`, which adds `-method foobar`
to the command line.

Instead of writing all the output to stdout also, use `-verbose` which
gives output like:

```
      Wasm.Build.Tests.WasmBuildAppTest.InvariantGlobalization(config: "Debug", aot: False, invariantGlobalization: null) [STARTING]
  ============== wasm test =============
  ============== wasm test-browser =============
      Wasm.Build.Tests.WasmBuildAppTest.InvariantGlobalization(config: "Debug", aot: False, invariantGlobalization: null) [FINISHED] Time: 8.6357275s
```

We log the detailed output to files anyway.

Co-authored-by: Mitchell Hwang <mitchhwang1418@gmail.com>

Co-authored-by: Mitchell Hwang <mitchhwang1418@gmail.com>

Instead, this is moved to a different AOT PR.

Revert "[wasm] Disable il stripping completely"

This reverts commit 25c2340.

This is needed because `mono-cil-strip` isn't available on helix. And we
want to disable cil stripping anyway.

This reverts commit ead13ee.