docs(changelog): changelog for v2.12 release

Generated this change-log using below command:
npm run release -- --skip.commit --skip.tag --release-as 2.12.0

Change-Id: Idb74f6a31bf2691e7666e2738030d6f0e2b8c519
Signed-off-by: Govindraj Raja <govindraj.raja@arm.com>
7 files changed