system variable: add tidb_enable_rate_limit_action  (#4975)
system variable: add tidb_enable_rate_limit_action  (#4975)

* add sys

Signed-off-by: Song Gao <f222f204032533a6fcbe6e5ff6aed541ec6b4541@163.com>

* address the comment

Signed-off-by: Song Gao <f222f204032533a6fcbe6e5ff6aed541ec6b4541@163.com>

* address the comment

Signed-off-by: Song Gao <f222f204032533a6fcbe6e5ff6aed541ec6b4541@163.com>

* address the comment

Signed-off-by: Song Gao <f222f204032533a6fcbe6e5ff6aed541ec6b4541@163.com>

* address the comment

Signed-off-by: Song Gao <f222f204032533a6fcbe6e5ff6aed541ec6b4541@163.com>

* address the comment

Signed-off-by: Song Gao <f222f204032533a6fcbe6e5ff6aed541ec6b4541@163.com>

* Apply suggestions from code review

Co-authored-by: TomShawn <3d0966147538bc5ab020e8dffa2c0b746f9728a6@users.noreply.github.com>

Co-authored-by: TomShawn <3d0966147538bc5ab020e8dffa2c0b746f9728a6@users.noreply.github.com>
pingcap/docs-cn,pingcap/docs-cn