[cryptolib] entropy driver

The Entropy driver aims to provide the following services:

• Interface to software csrng instance #14372
• Interface to pre-conditioned entropy provided by the entropy_src
• csrng KAT interface. See https://github.com/lowRISC/opentitan/blob/a82c4892e88253924b3f7af05ce7494232ab263a/sw/device/lib/crypto/drivers/entropy_kat.c#L115
• entropy_src pre-conditioner (SHA3-384) KAT interface.
• #14364
• edn0 and edn1 helper routines to configure entropy for countermeasures and FIPS entropy source for otbn. See https://github.com/lowRISC/opentitan/blob/a82c4892e88253924b3f7af05ce7494232ab263a/sw/device/lib/crypto/drivers/entropy.c#L319
• Health checks and error handling.
• Health test configuration hardening (entropy_src), as those registers are not shadowed. Done as part of #29701 but not yet cherry-picked to master.

From a FIPS perspective, KAT tests will be required for algorithms within scope of potential certifications. It may be possible to implement such tests at a higher level of abstraction, but planning to add them along with the driver as optional libraries to drive basic functional test cases.