interpreter_main compare should default to none

**Describe the bug**

By default `interpreter_main` set `--compare` to `jit` which end up compare every test result of the dslx interpreter w/ the jit'ed version of the same function.

While this is useful when working on the toolchain to verify that a given change has no impact on the JIT (or ir conversion), in practice this has little value to the developer as they are likely to only care about one result.

**To Reproduce**
```
bazel test //xls/examples/...
```

**Expected behavior**

The default should be `--compare=none` for both `interpreter_main` and `dslx_test` bazel rule, so that it only run the tests thru the interpreter.