func PadLeftSpace(s string, size int) string {
	return PadLeftChar(s, size, ' ')
}
PadLeftChar left pad a string with space character(' ') in a larger string(specified size).
if the size is less than the param string, the param string is returned.
note: size is unicode size.
package stringx
import (
	"errors"
	"math"
	"strings"
	"unicode/utf8"
	"github.com/bytedance/gopkg/internal/hack"
	"github.com/bytedance/gopkg/lang/fastrand"
)
var (
	ErrDecodeRune = errors.New("error occurred on rune decoding")
)
func PadLeftChar(s string, size int, ch rune) string {
	return padCharLeftOrRight(s, size, ch, true)
}