R1:49483bdb4823

Use "%P" to protect session key hashes in SessionEngine queries from DarkConsole

Summary:
Ref T6960. Ref T13217. Ref T13216. Depends on D19811. Use the recently-introduced "%P" conversion ("Password/Secret") to load sessions in SessionEngine.

This secret isn't critical to protect (it's the //hash// of the actual secret and not useful to attackers on its own) but it shows up on every page in DarkConsole and is an obvious case where `%P` is a more appropriate conversion.

Test Plan:
Note "*********" in the…