Add unit tests for length encoded integer related functions
Add unit tests for length encoded integer related functions

methane/mysql,sunjian1/mysql,Vorstack/mysql,henrylee2cn/mysql,rafaeljusto/mysql,siriele/mysql,nanata1115/mysql,beego/mysql,helight/helight_code,hebihui/mysql,eklitzke/mysql,segmentio/mysql,helight/helight_code,yyljlyy/mysql,bookerzzz/mysql,helight/helight_code,helight/helight_code,bookerzzz/mysql,roth1002/mysql,hyperworks/mysql,LightKool/mysql-go,segmentio/mysql,chinanjjohn2012/mysql,Frca/mysql,jockchou/mysql,helight/helight_code,go-sql-driver/mysql,VividCortex/mysql,VividCortex/mysql,Freeaqingme/golang-sql-driver-mysql,Go-SQL-Driver/MySQL,tmulchay/mysql,helight/helight_code,rlowe/mysql,helight/helight_code,helight/helight_code,springning/mysql,joshuaprunier/mysql,yonglehou/mysql,wfxiang08/mysql,zhgo/mysql,eXcomm/gomysql,methane/mysql,helight/helight_code,aperera/mysql,cw2018/mysql,cxflag203/mysql,netroby/mysql,muthusubbu459/mysql,LightKool/mysql-go