feat: Create a grouping utility that only parses new events

[Assem-Uber]

Summary
The existing grouping utility needs to process all events for each new page received. Also it does the same on each periodical fetching of pending activities. This computation is costly and degrades the web page performance. Solution is to have a new utility that can have events list and only add the new ones to the existing events group.

Changes

• Created a new WorkflowHistoryGrouper helper
• It accepts a list of events and only process newly added events
• Newly added events are split into small batches to control processing load.
• Pending activities/Decision can be updated on existing groups list
• If an entry exists in pending activity and does't have a corresponding group yet it is buffered until the group exists

New grouper is not integrated into history page, this will be done in the upcomming PR.