This migrates the last failing test for https://github.com/flutter/engine/pull/54981. In order to effectively resolve that test I had to make `equalsIgnoringHashCodes` more usable by printing out the line that differs instead of just a huge blob of "expected" vs "actual.
## example
Here's the output after the change.
### test
```
test('equalsIgnoringHashCodes - wrong line', () {
expect(
'1\n2\n3\n4\n5\n6\n7\n8\n9\n10',
equalsIgnoringHashCodes('1\n2\n3\n4\n5\n6\na\n8\n9\n10'),
);
});
```
### output
```
Expected: normalized value matches
'1\n'
'2\n'
'3\n'
'4\n'
'5\n'
'6\n'
'a\n'
'8\n'
'9\n'
'10'
Actual: '1\n'
'2\n'
'3\n'
'4\n'
'5\n'
'6\n'
'7\n'
'8\n'
'9\n'
'10'
Which: Lines 7 differed, expected:
'a'
but got
'7'
```
b5ce70a760