[legacy] clean up legacy code (#4743)
* [legacy] remove outdated codes of pipeline (#4692)
* [legacy] remove cli of benchmark and update optim (#4690)
* [legacy] remove cli of benchmark and update optim
* [doc] fix cli doc test
* [legacy] fix engine clip grad norm
* [legacy] remove outdated colo tensor (#4694)
* [legacy] remove outdated colo tensor
* [test] fix test import
* [legacy] move outdated zero to legacy (#4696)
* [legacy] clean up utils (#4700)
* [legacy] clean up utils
* [example] update examples
* [legacy] clean up amp
* [legacy] fix amp module
* [legacy] clean up gpc (#4742)
* [legacy] clean up context
* [legacy] clean core, constants and global vars
* [legacy] refactor initialize
* [example] fix examples ci
* [example] fix examples ci
* [legacy] fix tests
* [example] fix gpt example
* [example] fix examples ci
* [devops] fix ci installation
* [example] fix examples ci
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