Add missing test coverage for `SidecarMetadata`

### Problem

There was no test that failed when `RecordStreamFile`'s were created with missing `SidecarMetadata`.

We only caught this in in the integration env.

### Solution

Add unit **and** EET tests that validate `SidecarMetadata`.

### Alternatives

_No response_

Start by locating RecordStreamFile and SidecarMetadata, then inspect existing unit and EET tests for related validation. Done means adding unit and EET coverage that detects RecordStreamFile instances created without SidecarMetadata.

Written by the indexing model from the issue text.