runtime: do not use a relative import in testdata
runtime: do not use a relative import in testdata

Relative imports do not work in module mode. Use a fully-qualified
import path instead.

Updates #30228

Change-Id: I0a42ffa521a7b513395e7e1788022d24cbb1f31a
Reviewed-on: https://go-review.googlesource.com/c/go/+/165817
Run-TryBot: Bryan C. Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Jay Conrod <f3fadaedc813344da5ec13b41e26596889cc5baa@google.com>

nawawi/go,nawawi/go,josharian/go,akutz/go,CAFxX/go,akutz/go,akutz/go,CAFxX/go,cloudflare/go,cloudflare/go,nawawi/go,nawawi/go,cloudflare/go,cloudflare/go,nawawi/go,CAFxX/go,golang/go,golang/go,nawawi/go,cloudflare/go,golang/go,CAFxX/go,golang/go,akutz/go,golang/go,cloudflare/go,josharian/go,josharian/go,CAFxX/go,josharian/go,CAFxX/go,golang/go,golang/go,akutz/go,josharian/go,nawawi/go,CAFxX/go,josharian/go,nawawi/go,akutz/go,golang/go,cloudflare/go,josharian/go,akutz/go,CAFxX/go,akutz/go,josharian/go,cloudflare/go