* input: simplify internal implementation

remove currentValue, strictly follow one-way data flow
hack for MSIE input event when placeholder is set
remove isKorean hack (#11665, #10648)

* input-number: fix for new el-input

* test: input, fix vue warning

* date-time-range: fix for new el-input

* pagination: fix for new el-input, simplify internals

* input: fix input event on compositionend

* input-number: fix for new el-input

* input-number: nuke userInput on change