br: self protection enhancement

[BornChanger]

Enhancement

via this issue, kinds of br self protection methods are tracked

storage node out of disk

1. precheck available disk of tikv/tiflash nodes before restore br: prevent out of disk during restore #54316
2. check available disk against tikv before download sst files br: pre-check TiKV disk space before download tikv/tikv#17238

br node oom

1. self adaptive GOMEMLIMIT set to br task br: set memory limit #53793

overwrite existing tables

1. prevent restore sql statement at table level from overwriting existing table br: Add pre-check of duplicate table in the downstream #55044

write coming while restore is active

1. make table invisible while its restore is on-going br: make table invisible to user during lightning/ restore execution #52476

stuck of safe point advantage

1. pause log task if the global checkpoint lag is too large br: Enable checkpoint advancer to pause tasks lagged too large #51441