internal/coverage/cfile: remove more //go:linkname usage

internal/coverage/cfile: remove more //go:linkname usage

Move code so that basic imports work instead
of //go:linkname for metadata lists.

For #67401.

Change-Id: Id02075570befc45a9426559aad2137ab540928b2
Reviewed-on: https://go-review.googlesource.com/c/go/+/585915
Reviewed-by: Than McIntosh <thanm@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>