[request] API needs for Temporal Web

logging our future internal needs on github issue as discussed with @wxing1292 and @feedmeapples

Is your feature request related to a problem? Please describe.

there are a range of small things we want, which may involve the same underlying code:

• (small) ability to query OPEN + CLOSED workflows in a single call instead of currently double call
• (nice to have) backwards pagination of a query i/o just forward pagination
• API-side FILTER of event types in History (currently doing clientside)
• Given a parent workflow, find all the child workflows
  • (We want to make it easy to find the child workflows of a parent workflow in Temporal Web.)
  • having both pending and complete workflows would be best, but we can settle for just pending first.
  • Wenquan says implementation may be doable in mutableState if we only hold ID's of children
  • more info: https://www.notion.so/PRD-for-Parent-Child-workflows-on-Temporal-Web-69c3ed9654a9471e819c13398766b0a9

Describe the solution you'd like

we are unopnionated on solution but recognize that we may need to wait a while for the underlying code for this to be in place to offer these APIs.

No files or tests are named. Start by separating the four requested API capabilities and reading the linked Temporal Web PRD, then locate the existing query, history, and parent-child workflow API entry points. Done requires an agreed scope, API behavior, and acceptance criteria; the issue currently leaves the solution open.