Speed up CI

[Xuanwo]

Github now provides Actions Usage Metrics at https://github.com/apache/opendal/actions/metrics/usage

In the past 30 days, we have:

The most time consuming jobs are:

I believe we should take some actions to:

• build-haskell-doc at docs.yml
• test at ci_bindings_ocaml.yml
• build-ocaml-doc at docs.yml

So that we can save more times for other jobs.

[Xuanwo]

Thank you @XmchxUp for working on this, let's close since some slowest jobs have been addressed.