Stop using math/rand.Read and rand.Seed (deprecated in Go 1.20)

From golangci-lint:

> SA1019: rand.Read has been deprecated since Go 1.20 because it
>shouldn't be used: For almost all use cases, crypto/rand.Read is more
>appropriate. (staticcheck)

> SA1019: rand.Seed has been deprecated since Go 1.20 and an alternative
>has been available since Go 1.0: Programs that call Seed and then expect
>a specific sequence of results from the global random source (using
>functions such as Int) can be broken when a dependency changes how
>much it consumes from the global random source. To avoid such breakages,
>programs that need a specific result sequence should use
>NewRand(NewSource(seed)) to obtain a random generator that other
>packages cannot access. (staticcheck)

See also:

- https://pkg.go.dev/math/rand@go1.20#Read
- https://pkg.go.dev/math/rand@go1.20#Seed

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

pkg/seed/seed.go

@@ -14,6 +14,9 @@
    limitations under the License.
 */
 
+// Package seed provides an initializer for the global [math/rand] seed.
+//
+// Deprecated: Do not rely on the global seed.
 package seed
 
 import (
@@ -23,6 +26,8 @@ import (
 
 // WithTimeAndRand seeds the global math rand generator with nanoseconds
 // XOR'ed with a crypto component if available for uniqueness.
+//
+// Deprecated: Do not rely on the global seed.
 func WithTimeAndRand() {
 	var (
 		b [4]byte