Add `readObjectByName` method for Vault API (#1424)

## Description

This new endpoint matches the response of the existing ID-based read
method. Names have enforced uniqueness.

## Documentation

Does this require changes to the WorkOS Docs? E.g. the [API
Reference](https://workos.com/docs/reference) or code snippets need
updates.

```
[x] Yes
```

If yes, link a related docs PR and add a docs maintainer as a reviewer.
Their approval is required.

https://github.com/workos/workos/pull/49220