Move test runner to standard library.
Originated from #8819
# After Submitting
I'll update the documentation about testing:
http://www.nushell.sh/book/testing.html
---------
Co-authored-by: Mate Farkas <Mate.Farkas@oneidentity.com>
# Description
As in other testing frameworks, the `setup` runs before every test case,
and the `teardown` after that. A context can be created in `setup`,
which will be in the `$in` variable in the test cases, and in the
`teardown`. The `teardown` is called regardless of the test is passed,
skipped, or failed.
For example:
```nushell
use std.nu *
export def setup [] {
log debug "Setup is running"
{msg: "This is the context"}
}
export def teardown [] {
log debug $"Teardown is running. Context: ($in)"
}
export def test_assert_pass [] {
log debug $"Assert is running. Context: ($in)"
}
export def test_assert_skip [] {
log debug $"Assert is running. Context: ($in)"
assert skip
}
export def test_assert_fail_skipped_by_default [] {
log debug $"Assert is running. Context: ($in)"
assert false
}
```
# After Submitting
I'll update the documentation.
---------
Co-authored-by: Mate Farkas <Mate.Farkas@oneidentity.com>
