Add --config=asan test in CI

To make sure to not accidentally introduce memory leaks or invalid memory access issues, we should run the tests with AddressSanitizer in the CI (maybe as separate after successful 'regular' testing, as it can be quite a bit slower, and we should only run it after we know that the regular test execution passes).

The [.bazelrc already has the configuration](https://github.com/google/xls/blob/d2da1045eb2e55ac55a4bf3f1c8ef974244a2fd7/.bazelrc#L31-L38) prepared for this.

Context: PR #1443 would benefit from an ASAN run.