Implement batching CI project include context

What does this MR do and why?

As we did in #382531 (closed) / !108826 (merged) !109121 (merged), now we are implementing batching CI project include context for #382751 (closed).

Before this MR, we call

• Project.find_by_full_path for every file.
• project.commit.sha for every file.
• Ability.allowed? for every file.

Now, we call

• Project.where_full_path_in once.
• project.commit.sha once for the same project-sha pair.
• Ability.allowed? once for the same project.

The changes are behind a FF ci_batch_project_includes_context (#392746 (closed)).

MR acceptance checklist

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