[master < T1110] Add merge optimization to expand during runtime

[Josipmrden]

Expansion during runtime means that not always will the expansion be done from left to right according to EXPLAIN query, but depending on the previous executions and how many edges did we need to check on merge in order to see what's the fewest vector we need to expand.

[master < Task] PR

• Check, and update documentation if necessary
• Provide the full content or a guide for the final git message

To keep docs changelog up to date, one more thing to do:

• Write a release note here, including added/changed clauses
• Tag someone from docs team in the comments

[antoniofilipovic]

Looks good to me, made suggestion to push information on edge size to query::VertexAccessor level.