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/cache/cache.go

@@ -27,7 +27,7 @@ func createOnFirstUse() {
 		c = cache.New()
 		c.SetExpireDuration(ci.FsCacheExpireDuration)
 		c.SetExpireInterval(ci.FsCacheExpireInterval)
-		c.SetFinalizer(func(value interface{}) {
+		c.SetFinalizer(func(value any) {
 			if s, ok := value.(fs.Shutdowner); ok {
 				_ = fs.CountError(context.Background(), s.Shutdown(context.Background()))
 			}
@@ -98,7 +98,7 @@ func GetFn(ctx context.Context, fsString string, create func(ctx context.Context
 	createOnFirstUse()
 	canonicalFsString := Canonicalize(fsString)
 	created := false
-	value, err := c.Get(canonicalFsString, func(canonicalFsString string) (f interface{}, ok bool, err error) {
+	value, err := c.Get(canonicalFsString, func(canonicalFsString string) (f any, ok bool, err error) {
 		f, err = create(ctx, fsString) // always create the backend with the original non-canonicalised string
 		ok = err == nil || err == fs.ErrorIsFile
 		created = ok
@@ -149,9 +149,9 @@ func Pin(f fs.Fs) {
 //
 // This calls runtime.SetFinalizer on x so it shouldn't have a
 // finalizer already.
-func PinUntilFinalized(f fs.Fs, x interface{}) {
+func PinUntilFinalized(f fs.Fs, x any) {
 	Pin(f)
-	runtime.SetFinalizer(x, func(_ interface{}) {
+	runtime.SetFinalizer(x, func(_ any) {
 		Unpin(f)
 	})
 }