[rom/rom_ext] Add support for "hybrid" signature verification (PQC + traditional)

### Description

We would like to support dual signature verification for the transition to ROM_EXT and owner firmware. This means the image manifest needs to support two signatures, one for traditional and one for PCQ.

__Both__ signatures must be valid to execute the next stage. We want hybrid signature support to mitigate potential risk associated with finding a fatal flaw in a newer PCQ signature schemes.

This hybrid requirement applies to any place we use a PCQ key. As of writing this the following place we need this support are:
* [x] In ROM when verifying next ROM_EXT stage
* [ ] In ROM_EXT when verifying next Owner Firmware stage
* [ ] In ROM_EXT when verifying owner management commands (e.g. owner unlock)
* The Owner key and all derived keys (e.g. unlock key) need to be dual tranditional and PCQ keys