refactor `gomega` assertions

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### Problem

Currently, we're making use of [Gomega](https://onsi.github.io/gomega/) as a matcher library with [Ginkgo](https://onsi.github.io/ginkgo/), for making assertions in the tests. An example of such an assertion would be:

```go
func testSomething() {
err := doSomething()
gomega.Expect(err).Should(gomega.BeNil(), fmt.Sprint("failed to do something: %s", err.Error()))
}
```

The problem with using these directly in the tests would be that contributors now have to deal with learning the Gomega syntax for assertions, and also having too many of these look ugly and make the code less readable.

### Solution

We could create reusable helper functions that essentially act as wrappers around these assertions. For example

```go
func ExpectNil(item interface{}. annotation string) {
gomega.Expect(err).Should(gomega.BeNil(), message)
}

func testSomething() {
err := doSomething()
utils.ExpectNil(err, fmt.Sprintf("failed to do something: %s", err.Error()))
}
```

Start by locating the existing Gomega assertions in the test suite and review how Ginkgo tests currently report failures. Use the proposed reusable assertion wrappers as the scope, then update applicable tests and run the existing test suite to confirm behavior and readable failure messages remain intact.

Written by the indexing model from the issue text.