quic: add a config knob for congestion control algorithm

[danzh2010]

Right now the default is BBR and enabled by hard coding a QUICHE reloadable flag in
#19349 quic: enable BBR congestion control. But we want it to be configurable, especially distinguishable between upstream and downstream.
As discussed with @ggreenway, the preferred default value should be CUBIC, in consideration of https://en.m.wikipedia.org/wiki/TCP_congestion_control#TCP_BBR.

[github-actions]

This issue has been automatically marked as stale because it has not had activity in the last 30 days. It will be closed in the next 7 days unless it is tagged "help wanted" or "no stalebot" or other activity occurs. Thank you for your contributions.

[github-actions]

This issue has been automatically closed because it has not had activity in the last 37 days. If this issue is still valid, please ping a maintainer and ask them to label it as "help wanted" or "no stalebot". Thank you for your contributions.

[danzh2010]

need a non-stable tag and reopen