[DOCS-21046] refactor Explain Results page (#726)

* promotes "$sort and $group Stages" section

* moves "Execution Plan Statistics for Query with $lookup Pipeline Stage"

* merge queryPlanner sections

* moves sample tabs

* more merging

* queryPlanner sample output unsharded -- rework

* updates unsharded standalone queryPlanner sample output

* updates unsharded standalone queryPlanner sample output

* updates unsharded standalone queryPlanner sample output

* removes double quotes in output samples

* stage->STAGE

* updates nesting

* rearranging queryPlanner data items

* address nesting og queryPlan winningPlan

* updates indentation

* updates indentation

* updates sharded queryPlanner sample output

* save state

* save state

* adds inputStage table

* fixes list-table

* points executionStats.inputStage to queryPlanner.inputStage

* removes fields that are omitted starting in v5.1

* updates output examples

* fixes placeholder stage names

* correctly represent the queryPlan document in the output structure example

* inputStage ref updated

* removes g.txt

* updates analyze-query-plan

* removes versionadded 4.2 and fixes indentation

* adds inputStages

* table spacing fix

* tabbed interface

* versionadded spacing

* fixes tab ids

* merge top sections

* examples

* removes unnecessary example

* additional formatting

* updates output

* replaces missing ref

* review feedback

* fields may appear as a function of the query execution engine

* additional round of feedback

* tech review feedback

* clarify that root node is the final stage

* tech review updates

* move inputStage table to executionStats section

* move inputStage table to executionStats section

* updates explain.queryPlanner.winningPlan.queryPlan.inputStage

* update note to important admonition

* addressing feedback from product

* warning

Author: jmd-mongo