Added limit to projects and reduced batch size

What does this MR do and why?

Groups with huge no. of projects and subgroups are facing issue with statement timeout in group's audit event destination page, because of fetching all projects and subgroups at once.

Adding a limit of 20 projects for temporarily fixing the issue, as the users are not able to access the page. Meanwhile we will be working on a longterm fix in #438351 (closed) for fetching projects and groups in async.

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Related to #437282 (closed)