Use the serializer context to get an element's corpus

Requires !1305 (merged), Closes #700 (closed)

This removes some remnants of the old ListElements in which filtering by corpus was only optional, and uses the fact that all elements in ListElement{s,Children,Parents} are now of the same corpus to use the serializer context to send the corpus instead of retrieving the same corpus dozens of times in an SQL JOIN.

This removes an entire Hash Join on all the retrieved elements before the LIMIT is applied, shaving off 15% of the endpoint execution time on GoLFor (a corpus with 4 million elements on my local DB).

changed the description

added 4 commits

• 4177ee40...bfa34219 - 3 commits from branch master
• 2eb485e1 - Use the serializer context to get an element's corpus

Compare with previous version

requested review from @babadie

added 4 commits

• 81233b5d - Add an assertExactQueries on ListElements
• 01094851 - Release the Kraken
• d7899283 - Use the serializer context to get an element's corpus
• 8395cf80 - Update for assertExactQueries

Compare with previous version

changed the description

resolved all threads

mentioned in merge request !1306 (merged)

added 7 commits

• 8395cf80...8ce7ccde - 5 commits from branch master
• fb18bf98 - Use the serializer context to get an element's corpus
• 3c728bd0 - Update for assertExactQueries

Compare with previous version

resolved all threads

added 6 commits

• 3c728bd0...6f932ee3 - 4 commits from branch master
• 09fb5992 - Use the serializer context to get an element's corpus
• 78fb256a - Update for assertExactQueries

Compare with previous version

resolved all threads

added 4 commits

• 78fb256a...32715c0c - 2 commits from branch master
• 485f5ee7 - Use the serializer context to get an element's corpus
• af875d51 - Update for assertExactQueries

Compare with previous version

resolved all threads

added 6 commits

• af875d51...c4d880ee - 4 commits from branch master
• 8482bdb8 - Use the serializer context to get an element's corpus
• 1b58db7b - Update for assertExactQueries

Compare with previous version

resolved all threads

added 16 commits

• 1b58db7b...85f21724 - 14 commits from branch master
• 90bf0e72 - Use the serializer context to get an element's corpus
• 4b47847a - Update for assertExactQueries

Compare with previous version

mentioned in commit 244b7ac3

merged