Before, there was a `log/buffer.go`, but that design is not general, and
it introduces a lot of irrelevant `Content() (string, error) ` and
`return "", fmt.Errorf("not supported")` .
And the old `log/buffer.go` is difficult to use, developers have to
write a lot of `Contains` and `Sleep` code.
The new `LogChecker` is designed to be a general approach to help to
assert some messages appearing or not appearing in logs.
Change all license headers to comply with REUSE specification.
Fix#16132
Co-authored-by: flynnnnnnnnnn <flynnnnnnnnnn@github>
Co-authored-by: John Olheiser <john.olheiser@gmail.com>
