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

backend/mailru/mailru.go

@@ -901,7 +901,7 @@ func (t *treeState) NextRecord() (fs.DirEntry, error) {
 		return nil, nil
 	case api.ListParseUnknown15:
 		skip := int(r.ReadPu32())
-		for i := 0; i < skip; i++ {
+		for range skip {
 			r.ReadPu32()
 			r.ReadPu32()
 		}
@@ -1768,7 +1768,7 @@ func (f *Fs) eligibleForSpeedup(remote string, size int64, options ...fs.OpenOpt
 func (f *Fs) parseSpeedupPatterns(patternString string) (err error) {
 	f.speedupGlobs = nil
 	f.speedupAny = false
-	uniqueValidPatterns := make(map[string]interface{})
+	uniqueValidPatterns := make(map[string]any)
 
 	for _, pattern := range strings.Split(patternString, ",") {
 		pattern = strings.ToLower(strings.TrimSpace(pattern))
@@ -2131,10 +2131,7 @@ func getTransferRange(size int64, options ...fs.OpenOption) (start int64, end in
 	if limit < 0 {
 		limit = size - offset
 	}
-	end = offset + limit
-	if end > size {
-		end = size
-	}
+	end = min(offset+limit, size)
 	partial = !(offset == 0 && end == size)
 	return offset, end, partial
 }