bicep test returns exit code 0 when compilation fails

**Bicep version**

Built from the main branch at commit 6cff656e29547654af36e260634cf2de9ce63820.

**Describe the bug**

`bicep test` returns exit code `0` when the input file has compilation errors. It also reports that all evaluations passed. This can cause a CI job to pass even though the test file could not be compiled. I expected the command to return a non-zero exit code and not report a successful test run.

**To Reproduce**

Create a `bicepconfig.json` file:

```json
{
"experimentalFeaturesEnabled": {
"testFramework": true,
"asserts": true
}
}
```

Create a `main.bicep` file:

```bicep
test foo 'missing.bicep' = {}
```

Run:

```console
bicep test main.bicep
echo $?
```

The command reports `BCP091` followed by:

```text
All 0 evaluations passed!
```

The exit code is `0`.

**Additional context**

`TestCommand.RunAsync` logs the compilation diagnostics but only uses `testResults.Success` to determine the exit code. When the referenced test file cannot be loaded, no test result is added. An empty result set is then considered successful.

I can submit a fix and regression test for this.

Start with TestCommand.RunAsync and trace how compilation diagnostics and testResults.Success determine the command's exit status. Reproduce the missing.bicep case from the issue, then add a regression test showing compilation failure returns non-zero and does not report a successful run.

Written by the indexing model from the issue text.