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/pool/reader_writer_test.go

@@ -355,10 +355,7 @@ func (r *testReader) Read(p []byte) (n int, err error) {
 	if len(r.data) == 0 {
 		return 0, io.EOF
 	}
-	chunkSize := r.chunkSize
-	if chunkSize > len(r.data) {
-		chunkSize = len(r.data)
-	}
+	chunkSize := min(r.chunkSize, len(r.data))
 	n = copy(p, r.data[:chunkSize])
 	r.data = r.data[n:]
 	return n, nil
@@ -405,10 +402,7 @@ func TestRWBoundaryConditions(t *testing.T) {
 	write := func(rw *RW, data []byte, chunkSize int) {
 		writeData := data
 		for len(writeData) > 0 {
-			i := chunkSize
-			if i > len(writeData) {
-				i = len(writeData)
-			}
+			i := min(chunkSize, len(writeData))
 			nn, err := rw.Write(writeData[:i])
 			assert.NoError(t, err)
 			assert.Equal(t, len(writeData[:i]), nn)