[nrf noup] Support for ed25519 signature verification using ITS

[nordic-mik7]

Thic PR introduces support for ed25519 signature verification when CONFIG_NCS_BOOT_SIGNATURE_USING_ITS is set (through PSA API).

[de-nordic]

No.
Rename the kmu_key_ids to key_ids or whatever common name there can be made, and name the both lists the name, just choose one by selected secure storage.
Reduce all the changes, in the ifdef from, by moving all required compile time logic into one place, above all the usage cases.
Add common cpp identifiers for key count and secure storage usage.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[ahasztag]

No. Rename the kmu_key_ids to key_ids or whatever common name there can be made, and name the both lists the name, just choose one by selected secure storage. Reduce all the changes, in the ifdef from, by moving all required compile time logic into one place, above all the usage cases. Add common cpp identifiers for key count and secure storage usage.

Michał is on vacation so I will continue work on this PR. Changed as you've suggested.