If we start the covctrs blob at an odd alignment, then covctrs will
not be correctly aligned. Each individual entry is aligned properly,
but the start marker may be before any padding inserted to enforce
that alignment.
Fixes #58936
Change-Id: I802fbe40eacfa5a3c8c4864e078b0e078da956d5
Reviewed-on: https://go-review.googlesource.com/c/go/+/733740
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Cherry Mui <cherryyz@google.com> Reviewed-by: Keith Randall <khr@google.com>