Add Smctr extension and SCTRCLR instruction

[syedowaisalishah]

Description

• Added the Smctr extension, which includes Control Transfer Record management in Machine and Supervisor modes.
• Added the SCTRCLR instruction to clear the CTR buffer and reset related registers.

Fixes issue #512.

[ThinkOpenly]

Unfortunately, this is a duplicate of #554.

#554 should've mentioned #512 somewhere so a reference would be put in #512.

[syedowaisalishah]

I understand now that #573 is a duplicate of #554, and I appreciate the clarification. Should I go ahead and close #573?

[dhower-qc]

Yes, let's close this one. My bad on not assigning myself to the issue. I will be more diligent about that going forward.

[syedowaisalishah]

Thanks for the confirmation! No worries at all. I'll make sure to stay on top of the issue moving forward as well.