Add `cancel_intermediate_builds` to all buildkite pipelines

A few pipelines have `cancel_intermediate_builds` set, which cancels running jobs when new commits are pushed to existing branches. I think we should enable this for all pipelines to reduce CI queuing, which is especially helpful for macOS CI. I would also recommend we set `cancel_intermediate_builds_branch_filter = '!master'` (or `!main`) to make sure this doesn't apply to the default branch

Start by locating the Buildkite pipeline definitions and comparing the pipelines that already set `cancel_intermediate_builds`. Apply the requested setting across all pipelines while excluding the default branch with the proposed branch filter, then verify the CI configuration reflects both requirements.

Written by the indexing model from the issue text.