Add support for self-signed FMC_Alias CSR

[fdamato]

To facilitate Owner Identity Transfer, it's necessary for the Caliptra Runtime Firmware to offer an API that yields a self-signed CSR, ideally of the IDEVID. This would enable the Owner PKI to endorse the complete Device Certificate Chain using their own Certificate Authority.

At present, Caliptra 1.2 ROM only produces a self-signed IDEVID CSR when the "mfg_flag_gen_idev_id_csr" is activated.
The aim of this request is to extend CSR support to Caliptra 1.1 ROM integrators.

There are two potential methods to achieve this.

Option 1:
- At cold boot, Caliptra FMC should consistently generate an FMC_ALIAS CSR, self-sign it, and save it in persistent memory.
- Caliptra Runtime Firmware should introduce a new API to access the FMC_ALIAS CSR signed by the FMC.

Option 2:
- At cold boot, Caliptra FMC should consistently generate an FMC_ALIAS CSR, self-sign it, and store its signature in persistent memory.
- Caliptra Runtime Firmware should introduce a new API to rebuild the FMC_ALIAS CSR (utilizing its signature created by the FMC and saved in persistent memory).

While Option 2 might add a slight increase in complexity to the Runtime Firmware, it could potentially save a few bytes in persistent memory.