Remove redundant and expensive posting warmup

[rdettai-sk]

Description

Correlations (lookup of a list of event.id) use a huge amount of bandwidth.

• event.id is pretty much random, so its term dict is huge (2% of the total split size)

Some user queries that use terms queries are also excessively slow.

• when using a terms query in a dynamic field
  • the whole _dynamic term dict is warmed up (acceptable, 0.05% of the split size)
  • the whole _dynamic postings list is warmed up (prohibitive, 10% of split size)