Many of the testdata files were generated a long time ago with very old
versions of Go. The Go test output has changed over time, and these test
inputs no longer reflect the current state. The intention is to fully
support the test output of the most recent Go versions.
This commit also includes the source used to generate the test output,
so the output can be more easily updated in the future.
There was some code duplication between the go-junit-report binary, its
tests and the testdata/generate-golden script. This has been moved into
an internal package. The go-junit-report binary can now just focus on
flag parsing and validation, and it should be less likely that the
binary, tests and golden report generator behave differently.
