Introduce bug life cycle documentation.

Document what is expected during:
* triaging
* actively working on a bug
* closing/resolving

Also document how we maintain:
* product/component breakdown
* default-cc lists per component

Differential Revision: https://reviews.llvm.org/D53691


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@346299 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed