Standardize doc building workflows

[vyasr]

We use Sphinx to build our Python docs (and in the case of raft and cudf, also the C++ docs using breathe). Sphinx docs mention that builds may be done by directly invoking sphinx-build, but the sphinx-quickstart program that projects use to initialize a Sphinx doc tree creates a Makefile, and using make mentioned immediately afterwards in the official Sphinx docs. Almost all projects using Sphinx in the wild use make html rather than invoking sphinx-build directly. This is also typically reflected in their contributing guides for new developers. Using the Makefile is especially valuable because it centralizes the sphinx-build options to use so that building in different environments produces the same result. These issues are discussed in greater depth at rapidsai/cudf#13789 (comment).

Currently RAPIDS libraries are not so consistent about this. We mostly use sphinx-build directly in our ci/build_docs.sh scripts because that was chosen during the Jenkins->GH actions transition. Meanwhile, a few build.sh scripts support building docs, some with make and others with sphinx-build.

We should standardize all of our build scripts across different repositories to consistently use make.