Simplify Ubuntu CI using matrix strategy

[shrijitsingh99]

As per discussions in #3595
Currently using private docker images, will update it to PCL images before PR as PCL images lack clang currently.
Ubuntu CI: Link

[kunaltyagi]

🚀

Note: Needs Azure maintainer to

1. update the docker image
2. change the filename for the Ubuntu pipeline

before PR

PS: You need to change the docker image to the official one (it wouldn't fail since it doesn't run, how fun)

[shrijitsingh99]

PS: You need to change the docker image to the official one (it wouldn't fail since it doesn't run, how fun)

Have done it for now. If more changes are needed and have to be tested will do it on another branch with private images.

[taketwo]

Clang is disabled for the time being, so we don't need to update the Docker image. Could you update the PR to switch back to the official images? Then we merge and I update Azure?

[shrijitsingh99]

Clang is disabled for the time being, so we don't need to update the Docker image. Could you update the PR to switch back to the official images? Then we merge and I update Azure?

Have already switched back to official images in 2fd357b. Should i remove clang from the Dockerfile too?

[taketwo]

I'm fine having clang in the Docker image, will make future experiments easier without the need to switch to private Dockerhub.

[taketwo]

LGTM, please resolve the conflict and squash everything into one or two commits, as you prefer.

[shrijitsingh99]

LGTM, please resolve the conflict and squash everything into one or two commits, as you prefer.

Done

[taketwo]

Merged and updated Azure settings. Could you please send a follow-up PR updating the corresponding badge in the README.md?