Request for SBI Message Priority Support in overload manager

*Title*: Request for SBI Message Priority Support

*Description*:
In the 5G Core (5GC) network, the SBI Message Priority header (known as "3gpp-Sbi-Message-Priority") is a custom HTTP/2 header used to signal the relative importance of a signaling message. The header has a value of [0,31] representing the priority and it is documented in the spec [3GPP TS 29.500](https://www.etsi.org/deliver/etsi_ts/129500_129599/129500/18.06.00_60/ts_129500v180600p.pdf) .
Internally we (and I presume other telcos 😄 ) have the need to support overload handling based on such header so that we can define different thresholds for each priority depending on how important they are.
We focus mostly on stopreq overload actions.

Our custom handling where we defined custom overload stopreq actions and the decision flow for upcoming request looks somewhat like this:

Do you think it makes sense to have some kind of priority-aware shedding within the current Envoy ecosystem, or are there existing/planned features that we should be leveraging instead?
We are open to refining our custom handling into a standard contribution if this is a capability the community would find valuable as a whole.