In order to facilitate debuging and manual test flows for ownerhsip transfer,
we allow the owner pages to be erased if and only if the chip is in the DEV
lifecycle state AND the ROM_EXT was specifically built to allow owner erase.

Signed-off-by: Chris Frantz <[email protected]>
(cherry picked from commit a14571e)

1. Generate owner and application keys for the `SiVal` user in the
   CloudKMS instance.  Export the public components of those keys to the
   codebase (see
   `sw/device/silicon_creator/rom_ext/sival/keys/README.md`).
2. Add the keys to the appropriate exec_envs.
3. Add a config setting `//signing:owner_key_type` for selecting between
   RSA and ECDSA keys (RSA keys are for the currently released ROM_EXT
   0.4).

Signed-off-by: Chris Frantz <[email protected]>
(cherry picked from commit b3af7c1)

1. Create `dummy` ECDSA application keys for ownership transfer tests.
2. Delete `dummy` RSA application keys.

Signed-off-by: Chris Frantz <[email protected]>
(cherry picked from commit 2a8092f)