config: fix problem reading pasted tokens over 4095 bytes

Before this change we were reading input from stdin using the terminal
in the default line mode which has a limit of 4095 characters.

The typical culprit was onedrive tokens (which are very long) giving the error

    Couldn't decode response: invalid character 'e' looking for beginning of value

This change swaps over to use the github.com/peterh/liner read line
library which does not have that limitation and also enables more
sensible cursor editing.

Fixes #8688 #8323 #5835

fs/config/ui_test.go

@@ -85,9 +85,9 @@ func testConfigFile(t *testing.T, options []fs.Option, configFileName string) fu
 
 // makeReadLine makes a simple readLine which returns a fixed list of
 // strings
-func makeReadLine(answers []string) func() string {
+func makeReadLine(answers []string) func(string) string {
 	i := 0
-	return func() string {
+	return func(string) string {
 		i++
 		return answers[i-1]
 	}