Update elastic fields from integer to long

The following discussion from !171704 (merged) should be addressed:

From @terrichu: I see a few mismatches that need to be adjusted. It looks like almostt all of the ignore_columns were recently updated to bigint in the database. That work should be in a follow up MR next milestone.

• target_project_id
• source_project_id
• author_id
• assignee_id
• noteable_id
• owner_id
• root_namespace_id
• project_id

TODO

• Update the field in Elastic::Latest::*Config or Search::Elastic::Types::* to the correct type
• Add a migration to reindex the affected indices (preferably one index at a time?)
• Also cross check all integer-type columns that are indexed into Elasticsearch and create follow-ups if more changes are needed

Plan

• notes: !182727 (merged) !184202 (merged) !189649 (merged)
• merge_requests: !182255 (merged) !188909 (merged)
• projects: !180165 (merged) !187003 (merged)
• [-] issues: Replaced by work items
• work_items: !189044 (merged) !190508 (merged) Follow up #549519 (closed)
• users: !180178 (merged) !182733 (merged)
• wikis: !180023 (merged)
• [-] epics: Replaced by work items
• [-] commits: !189653 (closed)
• Remove the ignored columns type check: context 'with foreign keys mappings'