[VAL] Check register file DCLS comparison

[nasahlpa]

Currently, there is no test that checks whether a fault injected into the main or shadow core register file gets detected by DCLS. Ideally, the following tests are written (DCLS is enabled & lockstep_regfile_enable enabled):

• Bit flip in the registers of the main or the shadow core register file
• Bit flip in the output ports of the main or the shadow core register file

Ideally, this test is written after #482 has been merged. This PR changes the RF DCLS lockstep mechanism. A fault is detected once the faulty RF value is read (either by the main or the shadow core).

[samipmodi323]

Re-assigning this to Ankita/Jinal as Ankita has developed test for bit flip for monitored register file. Jinal was working on all non-monitored register file.