v1.17: Show staked vs nonstaked packets sent down/throttled (backport of #600)

[mergify]

Problem

The current metrics cannot tell what are the portions of packets sent down and throttled from staked vs non-staked.

Summary of Changes

Add two metrics in streamer:

staked_packets_sent_for_batching
unstaked_packets_sent_for_batching
throttled_unstaked_streams
throttled_staked_streams

Fixes #

---

This is an automatic backport of pull request #600 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of b443cfb has failed:

On branch mergify/bp/v1.17/pr-600
Your branch is up to date with 'origin/v1.17'.

You are currently cherry-picking commit b443cfb0c7.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   streamer/src/nonblocking/quic.rs

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   streamer/src/quic.rs

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 64.28571% with 5 lines in your changes are missing coverage. Please review.

Project coverage is 81.6%. Comparing base (2199f6e) to head (429e15b).

Additional details and impacted files

@@            Coverage Diff            @@
##            v1.17     #613     +/-   ##
=========================================
- Coverage    81.6%    81.6%   -0.1%     
=========================================
  Files         806      806             
  Lines      219284   219298     +14     
=========================================
- Hits       179060   179034     -26     
- Misses      40224    40264     +40     

[brooksprumo]

Looks good to me. Please get approval from backport/release owners before merging.

[t-nelson]

lgtm