Intercept Power+Vol Up hotkey for SRE entry (C-side, OEM)

[kat-perez]

Detect Power + Volume Up hotkey combination during boot and route to the SRE boot path.

[kat-perez]

Proven on OEM platform via serial log #4: [SrePriorityBoot] [Bds] Vol+ -> SRE app dispatch then BDS expands FvFile(5A98F2C1-7D3B-4E8F-A124-B6E891D45C03) -> BpRecoveryLoaderApp.efi loaded, full SRE chainload follows.

Implementation: feature-gated via PcdSreHotkeyRoutingEnabled in DeviceBootManagerLib::DeviceBootManagerPriorityBoot. Other platforms using this lib inherit the same code but keep the FeaturePcd at FALSE default - no behavior change for them.

Patina-Rust equivalent tracked under the Patina Port (Investigation) milestone.