Adds opcodes for "unimp" and "c.unimp" unimplemented instructions.

These instructions will still generate invalid instruction exceptions,
but will not create log messages, as these are considered intentional
unimplemented instructions.

Also fixes an issue w.r.t. clearing and seeing status of breakpoints
on control-flow, interrupts, and exceptions for mpact-cheriot.

PiperOrigin-RevId: 720727822
Change-Id: I97364e87bf99c055c9496c9f17649e1d353291ca

mpact/sim/generic/operand_interface.h

diff --git a/mpact/sim/generic/operand_interface.h b/mpact/sim/generic/operand_interface.h
index 743a204..b71260a 100644
--- a/mpact/sim/generic/operand_interface.h
+++ b/mpact/sim/generic/operand_interface.h
@@ -64,7 +64,7 @@
   // Return a pointer to the object instance that implements the state in
   // question (or nullptr) if no such object "makes sense". This is used if
   // the object requires additional manipulation - such as a fifo that needs
-  // to be pop'ed. If no such manipulation is required, nullptr should be
+  // to be popped. If no such manipulation is required, nullptr should be
   // returned.
   virtual std::any GetObject() const = 0;