[WIP] Make page cacheable for render faster

Ideas:

• Use fragment cache View as much as possible, make sure cache block have nothing about user;
• Ensure model changes will touch the references model to update cache_key;
• Use Javascript or CSS to process the logic related user ability, move out of the cache block;
• Add second_level_cache

TODO List:

• Issues
• MergeRequests
• Milestones can not, there have a little counter in view
• Build CommitStatus
• Move MR ci_build status out of the cache block

Issue List

Before:

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After:

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