test: refactor unclear tests to composed matchers (#68674)
### What
Improve the test matcher for string matching while searching in array
case, those flaky tests were giving unclear failing messages without
enough context to help investigate the flakeness.
### Why
Example of existing unclear flaky failure
```
pnpm test test/integration/link-ref/test/index.test.js
• Invalid hrefs > production mode > should preload with child ref with React.createRef
Expand output
● Invalid hrefs › production mode › should preload with child ref with React.createRef
expect(received).toBe(expected) // [Object.is](http://object.is/) equality
Expected: true
Received: false
```
While looking at the test, assertions like `expect(found).toBe(true)`
could fail without telling us what are the context, what is the original
input before narrowing down as a boolean value. After changing to a
composed testing matcher, we're able to see what href links are giving
us the unexpected result
```ts
expect(hrefs).toEqual(
expect.arrayContaining([expect.stringContaining('index')])
)
```
For example, if we're looking for a string pattern `first-1` in the link
hrefs, but it only got `first`, the failure message would look like
this. This will help us identify the root cause easier with more
context.
```
● Prefetching Links in viewport › production mode › should prefetch with link in viewport onload
expect(received).toEqual(expected) // deep equality
Expected: ArrayContaining [StringContaining "first1"]
Received: ["/_next/static/chunks/pages/first-c9300691290bda9a.js"]
109 | links.map(async (link) => await link.getAttribute('href'))
110 | )
> 111 | expect(hrefs).toEqual(
| ^
112 | expect.arrayContaining([expect.stringContaining('first1')])
```
