build: modernize Go usage

This commit modernizes Go usage. This was done with:

go run golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize@latest -fix -test ./...

Then files needed to be `go fmt`ed and a few comments needed to be
restored.

The modernizations include replacing

- if/else conditional assignment by a call to the built-in min or max functions added in go1.21
- sort.Slice(x, func(i, j int) bool) { return s[i] < s[j] } by a call to slices.Sort(s), added in go1.21
- interface{} by the 'any' type added in go1.18
- append([]T(nil), s...) by slices.Clone(s) or slices.Concat(s), added in go1.21
- loop around an m[k]=v map update by a call to one of the Collect, Copy, Clone, or Insert functions from the maps package, added in go1.21
- []byte(fmt.Sprintf...) by fmt.Appendf(nil, ...), added in go1.19
- append(s[:i], s[i+1]...) by slices.Delete(s, i, i+1), added in go1.21
- a 3-clause for i := 0; i < n; i++ {} loop by for i := range n {}, added in go1.22

lib/random/random_test.go

@@ -8,7 +8,7 @@ import (
 )
 
 func TestStringLength(t *testing.T) {
-	for i := 0; i < 100; i++ {
+	for i := range 100 {
 		s := String(i)
 		assert.Equal(t, i, len(s))
 	}
@@ -16,7 +16,7 @@ func TestStringLength(t *testing.T) {
 
 func TestStringDuplicates(t *testing.T) {
 	seen := map[string]bool{}
-	for i := 0; i < 100; i++ {
+	for range 100 {
 		s := String(8)
 		assert.False(t, seen[s])
 		assert.Equal(t, 8, len(s))
@@ -41,7 +41,7 @@ func TestPasswordLength(t *testing.T) {
 
 func TestPasswordDuplicates(t *testing.T) {
 	seen := map[string]bool{}
-	for i := 0; i < 100; i++ {
+	for range 100 {
 		s, err := Password(64)
 		require.NoError(t, err)
 		assert.False(t, seen[s])