-shuffle seed should be displayed in the summary

[kevinawoo]

When using go test -shuffle=on ./..., this will print out a shuffle seed

Example output if there's a failure:

ok  	github.com/kevinawoo/test/pkg/example	0.686s
-test.shuffle 1655405871045329000
--- FAIL: TestExample (0.00s)
panic: runtime error: index out of range [99] with length 1 [recovered]
	panic: runtime error: index out of range [99] with length 1

The seed 1655405871045329000 allows us to reproduce the same test shuffle to reproduce failures.

go test -json -shuffle=on ./... output does show the shuffle seed, example:

{"Time":"2022-06-16T11:52:52.124788-07:00","Action":"output","Package":"github.com/kevinawoo/test/pkg/example","Output":"-test.shuffle 1655405871045329000\n"}

However when we run it go run gotest.tools/gotestsum@latest -- -shuffle=on ./..., the shuffle seed doesn't get printed out.

[dnephin]

Thank you for opening this issue! It looks like there will need to be special handling for a few of the formats.

• testname - does print the -test.shuffle line, but it's not clear exactly which package the line is associated with. Maybe it should only be printed on failure.
• pkgname (the default format) - does not print it on failure
• standard-quiet - prints it all the time, but shouldn't

The rest seem to do the right thing.

Since the output is associated with the package (not a specific test), I think we'll have to handle it similar to cached, and coverage. Store it on Package, and print it as part of the package output.