[cryptolib] Deduplicate the `ibex` driver

[pamaury]

Description

There are two ibex drivers:

• silicon_creator driver
• cryptolib driver

Also the silicon_creator has a rnd driver.

The following items (at least) should be looked at:

• ibex_rnd32_read: move to silicon_creator
• ibex_{enable,disable}_icache: move to silicon_creator
• ibex_check_security_config: keep in cryptolib
• ibex_clear_rf: keep in cryptolib
• create ibex mock
• expand ibex unittest
• maybe turn the cryptolib rv_core_ibex mock into a real mock

[nasahlpa]

Thanks Amaury for your analysis!

I would suggest:

• ibex_rnd32_read: move to silicon_creator
• ibex_{enable,disable}_icache: move to silicon_creator
• ibex_check_security_config: keep in CL
  ibex_clear_rf: keep in CL

The reason why I would keep ibex_check_security_config in the CL is that this function checks whether the device is set up correctly for a safe CL execution. However, we need to assume that in ROM and ROM_EXT this is true.

[pamaury]

Sounds good, I have updated the issue. I also added some items related to the unittests and mocking, as identified in #28646

[pamaury]

I also noticed that there is a rv_core_ibex mock in cryptolib but it is not a real google test mock. We might have to look at this as well to determine if this needs to be updated.