all: use Go 1.26 things, run most gofix modernizers

I omitted a lot of the min/max modernizers because they didn't
result in more clear code.

Some of it's older "for x := range 123".

Also: errors.AsType, any, fmt.Appendf, etc.

Updates #18682

Change-Id: I83a451577f33877f962766a5b65ce86f7696471c
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

ipn/store/awsstore/store_aws.go

@@ -189,8 +189,7 @@ func (s *awsStore) LoadState() error {
 	)
 
 	if err != nil {
-		var pnf *ssmTypes.ParameterNotFound
-		if errors.As(err, &pnf) {
+		if _, ok := errors.AsType[*ssmTypes.ParameterNotFound](err); ok {
 			// Create the parameter as it does not exist yet
 			// and return directly as it is defacto empty
 			return s.persistState()