Implement AsyncSearch Status API

[stevejgordon]

Main change to existing is removing Response from AsyncSearchResponseBase and making AsyncSearchResponseBase non-generic as a result. This allows the base to be used for the status response which differs by not include the response itself.

[stevejgordon]

@Mpdreamz - I've revised the approach to avoid the breaking change.

[Mpdreamz]

LGTM 👍

[github-actions]

The backport to master failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-master master
# Navigate to the new working tree
cd .worktrees/backport-master
# Create a new branch
git switch --create backport-5239-to-master
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick ---mainline 1 cebf2bd53cdfad124316ec0c53f4e6e0ff5ba786
# Push it to GitHub
git push --set-upstream origin backport-5239-to-master
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-master

Then, create a pull request where the base branch is master and the compare/head branch is backport-5239-to-master.