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

fs/rc/params_test.go

@@ -109,7 +109,7 @@ func TestParamsGetString(t *testing.T) {
 
 func TestParamsGetInt64(t *testing.T) {
 	for _, test := range []struct {
-		value     interface{}
+		value     any
 		result    int64
 		errString string
 	}{
@@ -152,7 +152,7 @@ func TestParamsGetInt64(t *testing.T) {
 
 func TestParamsGetFloat64(t *testing.T) {
 	for _, test := range []struct {
-		value     interface{}
+		value     any
 		result    float64
 		errString string
 	}{
@@ -193,7 +193,7 @@ func TestParamsGetFloat64(t *testing.T) {
 
 func TestParamsGetDuration(t *testing.T) {
 	for _, test := range []struct {
-		value     interface{}
+		value     any
 		result    time.Duration
 		errString string
 	}{
@@ -244,7 +244,7 @@ func TestParamsGetDuration(t *testing.T) {
 
 func TestParamsGetBool(t *testing.T) {
 	for _, test := range []struct {
-		value     interface{}
+		value     any
 		result    bool
 		errString string
 	}{