[PERF] Use binary search in positional posting list (#2424)

## Description of changes

*Summarize the changes made by this PR.*
 - Improvements & Bug fixes
- Uses binary search in PPL since entries are ordered, on a dataset of
1107 posting lists with ~450,000 doc ids, the aggregate time spent
inserting was taking ~100 seconds. This reduces it to .01 seconds. :)
 - New functionality
	 - none

## Test plan
*How are these changes tested?*
- [x] Tests pass locally with `pytest` for python, `yarn test` for js,
`cargo test` for rust

## Documentation Changes
None

Author: HammadB

rust/worker/src/blockstore/positional_posting_list_value.rs

@@ -20,7 +20,7 @@ impl PositionalPostingList {
     }
 
     pub(crate) fn get_positions_for_doc_id(&self, doc_id: i32) -> Option<Int32Array> {
-        let index = self.doc_ids.iter().position(|x| x == Some(doc_id));
+        let index = self.doc_ids.values().binary_search(&doc_id).ok();
         match index {
             Some(index) => {
                 let target_positions = self.positions.value(index);