* Fix the behavior when analyzing an individual instruction:
* exisiting instruction:
Clear the original records and re-analyze it as a new instruction.
* new instruction with exisiting result id:
Clear the original records of the exisiting result id. This means
the records of the analyzed result-id-defining instruction will be
overwritten by the record of the new instruction with the same
result id.
* new instruction with new result id or without result id:
Just update the internal records to incorperate the new
instruction.
* Add tests for analyzing individual instruction w/o an exisiting module.
* Refactor ClearInst() implementation
* Remove ClearDef() function.
* Fixed a bug in DefUseManager::ReplaceAllUsesWith() that OpName
instruction may trigger the assertion incorrectly.
* update the blurbs for EraseUseRecordsOfOperandIds()
