[BE] Move conda cmake installation to Docker (#87309)
This is parts of the effort to consolidate pip and conda installation in the CI to improve our CI reliability. This moves conda cmake installation to Docker in those use cases that require it:
* Ubuntu bionic and focal
On the other hand:
* XLA doesn't seem to need conda cmake anymore (Build and test successfully)
* Centos is not in used anywhere in the CI
Pull Request resolved: https://github.com/pytorch/pytorch/pull/87309
Approved by: https://github.com/ZainRizvi, https://github.com/malfet
